Title

Plain Non-Past Form: No Conjugation

All Keiyōshi 形容詞 end in the vowel /i/ い. This has given rise to the name "i-adjectives イ形容詞" in many textbooks, which is also occasionally used by Japanese grammarians to refer to this class of words.  

This い attaches to the stem (gokan 語幹), and it is the い that is dropped and replaced with other endings to make other conjugations. It itself is a conjugation. This base form of adjectives is used for its non-past form (hikakokei 非過去形), which we learned in Lessons 9-10 stands for both present tense (genzai jisei 現在時制) and future tense (mirai jisei 未来時制). However, in the case of adjectives, the non-past tense is only understood as being the present tense; producing a future tense interpretation would involve introducing other grammar points that are not adjectival in origin. As such, all non-past tense (hikako jisei 非過去時制) sentences in this lesson are, in fact, in the present tense.

We have already seen this basic non-past (unconjugated) form used in Exs. 1-3 above with the adjective 新しい. The base form of adjectives is used in plain speech or when directly modifying a noun. First, let's look at a handful of useful adjectives and see how they work in these two scenarios.

Because Japanese phrasing is so different, it would be wrong of you as the learner to simply learn adjectives with single-word equivalents. As will be the case for other example charts in this lesson, the goal will be to try to know about any important quirk(s) a word may have so that you actually get to learn how to truly understand it. 

Vocabulary Notes:

①Atsui 熱い means "hot" as in things whereas atsui 暑い means "hot" as in the weather.  There is no difference in pronunciation as both are enunciated with a LHL (low-high-low) pitch. Atsui 厚い means "thick" and is distinguished from these other adjectives by pitch with a LHH (low-high-high) pattern. 

② In addition to meaning "spicy," karai 辛い may also mean "salty." This is thought to be a dialect meaning by many speakers as it is mostly used in this sense by people in West Japan. However, the Standard Japanese expression is actually based on this, only adding the word for "salt" shio 塩 in the front to produce shiokarai 塩辛い. In writing if one were to use karai to mean "salty," 鹹い would be more 'correct,' but in actual practice, 辛い is the dominant spelling, and to make matters worse, speakers that use it to mean "salty" and "spicy" simply distinguish them in context. This means that you as the listener have to use your common sense to know what they're saying. If this weren't enough, most speakers in East Japan use a completely different word for "salty," and that word is shoppai しょっぱい.
③As an English speaker, you may be confused as to why hoshii 欲しい is in a list of adjectives if it means "to want," but in Japanese this word is an adjective. Verbs don't end in /i/. 

④At a basic understanding, tsumetai 冷たい means "cold" as in things whereas samui 寒い means "cold" as in "weather." 冷たい may also refer to "cold" personalities. What about the air or wind? 

Tsumetai kūki 冷たい空気　〇
Tsumetai kaze 冷たい風　〇

The reason for why 冷たい is used is because the air/wind touches the skin as a "thing." 寒い does have other meanings, but you are free to study those at a later point.

⑤Furui 古い means "old" in specific contexts. It literally refers to the state of a thing or situations being "old," but whereas it can be used to mean "old" in relation to feeling, food, behavior, etc., it isn't used to refer to old age. The phrases surrounding old age are actually rather complicated, so we'll study that topic separately later.

⑥Wakai 若い means "young" and is not as complicated. It refers to states that haven't been so for very long, which includes age, maturity, youthfulness, etc. 

⑦Akarui 明るい and kurai 暗い can both be used in the literal sense of "bright" and "dark" respectively, but they may also both be used figuratively similarly to how their English equivalents are.

⑧暖かい and 温かい are both read as atatakai. The first spelling is used in reference to the weather whereas the second spelling is used to refer to "warm" to the touch as well as in reference to emotion. This word can be a tongue twister even for native speakers, and so you may hear it pronounced occasionally as attakai あったかい.

⑨Suzushii 涼しい doesn't mean "cool" as in "cool person." This word is limited to the weather and referring to "clear/composed" emotions/eyes, etc. 

⑩Chiisai 小さい and ōkii 大きい are in many contexts to refer to size/scale. They can also refer to being "young/older" respectively. 

⑪As for the spelling and nuancing of hayai, when used to mean "early/quick," it is spelled as 早い. When strictly referring to speed, it may be spelled as 速い.
⑫Takai 高い refers both to height and things being expensive. When referring to the height of a person, it is seen in the set phrase se ga takai 背が高い. 

⑬Hikui 低い may refer to low as in rank, value, quality, position to the ground, etc. As such, it may mean "short," but when it is used in this sense, it is used in the set phrase se ga hikui 背が低い. It can also be used to refer to deep voices, the opposite being expressed by takai 高い.

⑭温い may be occasionally alternatively pronounced as ぬくい or even ぬくとい. 

Grammar Note:

There is no morphological difference between an adjective in its "attributive form" (the Rentaikei 連体形 ) and its predicative form (the Shūshikei 終止形). However, there are grammatical differences between the two that cannot be ignored, especially when building complex adjectival clauses that attach to nouns. As was mentioned before the chart of example words, adjectives only modify nouns directly in their plain forms. There is no such thing as a polite attributive form. Likewise, every other "plain" conjugation that an adjective has may either be in the front/middle (inside) of a sentence modifying a noun (as an attribute) or at the end of the sentence (as the predicate). 

1. クマは強い。
Kuma wa tsuyoi.
Bears are strong.

2. 人間は弱い生き物だ。
Ningen wa yowai ikimono da.
Humans are weak creatures.

3. 南米は暑い！
Nambei wa atsui!
South America is hot!

4. 手が熱い。
Te ga atsui.
My/your hands are hot.

5. あれは古い電話だ。
Are wa furui denwa da.
That is an old phone.

6. 水が冷たい。
Mizu ga tsumetai.
The water is cold.

7. 冬は寒い！
Fuyu wa samui!
Winter is cold!

8. あの店は安い。
Ano mise wa yasui.
That store is cheap (affordable).

How to make the non-past tense polite is a tricky yet easy topic. In Modern Japanese, the solution is simply to add desu です after the adjective, using です purely as a politeness marker. This grammar has only been around for a little over a century, and so people uptight with their grammar as well as a certain percentage of the older generations may still frown upon its use (in favor of older grammar), but this grammar is very much a part of everyday speech. 

Although there is no real conjugation involved, for those that prefer a visual aid and in order to give some more examples of adjectives, here is a chart showcasing the difference between plain and polite speech in the non-past tense. 

Vocabulary Notes:

①近い can be used in both a spatial and temporal sense. It can also be used to refer to "close" relationships and "close" relatives. It may also be used to describe degree. It is also used in the phrase for "to be nearsighted," which is me ga chikai 目が近い. 

②遠い can be used in both a spatial and temporal sense, refer to "distant" relationships and relatives, and "far (from)" in the sense of degree. It can refer to distant sounds and is also used in the phrase for "to be farsighted," which is me ga tōi 目が遠い.

③Utsukushii 美しい is a very refined word in the same way English speakers use the word "beautiful."

④Karui 軽い means "light" not just in reference to weight but also footing, importance, etc. 

⑤Omoi 重い means "heavy" in reference to both weight and emotion. It can also mean "serious" as in responsibility/situation as well as illness/punishment.
⑥Itai 痛い means "painful," but it also is used in situations where English speakers would likely use the verb "to hurt." It is also the interjection used for "ouch." Be careful with intonation. It should be pronounced with a LHL intonation. A LHH intonation results in the noun 遺体 meaning "dead body."

Grammar Note: 

Note that です is not added to an adjective when used before a noun because です DOES NOT have an attributive form. Expect it to always be at the end of the sentence.

12. 公園が近いです。
Kōen ga chikai desu.
There is a park is nearby.

13. 景色が美しいです。
Keshiki ga utsukushii desu.
The scenery is beautiful.

14. 仕事は楽しいです。
Shigoto wa tanoshii desu.
(My) work is fun. 

15. 足が痛い！
Ashi ga itai!
My feet hurt!

Vocabulary Notes:

①When used to mean "delicious," oishii may also be spelled as 美味しい. It also has the meaning of "attractive" in the sense of "favorable." 

②Mazui まずい means "bad" as in flavor, in which case it may also be spelled as 不味い. When used to mean "bad" as in "unskillful," it may be spelled as 拙い. It can also refer to "bad/awkward" situations, and in this situation, it is often used in the sense of "oh, no!"

③優しい and 易しい are both pronounced as "yasashii" with a LHHH intonation. 
④Usui 薄い is "thin" in relation to objects but never people, but it ironically can be used to refer to "thin/slim" chance. It may also refer to colors being "pale" or something being "dilute(d)" in a liquid. From this last meaning it can also mean "weak" as in taste. Think coffee. 
⑤Koi 濃い refers to the thickness (depth) of color, the thickness (density) of liquids, or the thickness (strength) of flavors, smells, possibilities, or relationships. Unlike atsui 厚い, it is never used to refer to the thickness of physical objects. Also, most speakers in West and South Japan pronounce this word as koyui 濃ゆい.

Grammar Note:

The attributive and predicative form of the plain past tense conjugation are the same. As seen in Ex. 24, it is more common to see the past tense used in the attributive form when it is a part of a larger modifying, dependent clause. However, this is not a requirement. 

16. ラーメンは美味しかったです。
Ramen wa oishikatta desu.
The ramen was delicious.

17. 仕事が忙しかった。
Shigoto ga isogashikatta.
Work was busy.

18. あの映画は楽しかったです。
Ano eiga wa tanoshikatta desu.
That movie was fun.

19. 彼が優しかった。
Kare ga yasashikatta.
He was kind.

20. 長谷川先生は厳しかったです。
Hasegawa-sensei wa kibishikatta desu.
Hasegawa-sensei was strict.

21. 道が狭かったです。
Michi ga semakatta desu.
The street(s) were narrow.

22. 元から成功の望みは薄かった。
Moto kara seikō no nozomi wa usukatta.
There was slim hope of success from the start.

23. 病院食はまずかったです。
Byōinshoku wa mazukatta desu.
The hospital meals were awful.

24. 味は若干濃かったです。
Aji wa jakkan kokatta desu.
The flavor was somewhat strong.

25. （お）弁当が美味しかった話
(O)bentō ga oishikatta hanashi
Talk of the bento having been delicious. 

Grammar Note: The prefix お- is attached to a number of nouns to make them sound softer/politer.  

①Hosoi 細い means "thin" as in "slender" and may be used in reference to people.
②Futoi 太い means "thick" as in "fat" and may also refer to a person's voice being "thick."

③Do not pronounce kawaii かわいい the same way as kowai 怖い. They are clearly separate words.
④Kowai 怖い may translate as "scary" or "scared," but this is due to the Japanese grammar being simpler than English. The word is only used from a personal perspective, so you yourself are scared of things that are scary.
⑤Words such as kanashii 悲しい, ureshii 嬉しい, sabishii 寂しい are by default first-person in nature. They may be used in second-person questions, but as for third person, they get changed up a bit (Lesson 100). 

⑥Sabishii 寂しい may also mean "desolate" when used in reference to places.

Negation is not limited to the predicative form. Meaning, you can use the negative form of an adjective in its attributive form. There is no change in morphology, but you can see a negative adjective be a part of a much larger dependent clause modifying a noun. 

26. 僕は蛇が怖くないよ。
Boku wa hebi ga kowakunai yo.
I'm not scared of snakes.
As for me, snakes aren't scary.

27. あの猫はかわいくはないよ。
Ano neko wa kawaiku wa nai yo.
That cat isn't scary (but does fit another description).

28. 僕は悲しくない。
Boku wa kanashikunai.
I'm not sad.

29. 操作は難しくない。
Sōsa wa muzukashikunai. 
Operating it isn't difficult.

30. 難しくない点もメリットのひとつです。
Muzukashikunai ten mo meritto no hitotsu desu.
The point of it not being difficult is also one of its merits.

Vocabulary Notes:

①Omoshiroi 面白い may also mean "funny" and it is often pronounced as omoroi おもろい in West Japan.
②Tadashii 正しい may also mean "just/proper." 
③Aoi 青い may be used in both the sense of "blue" and "green." The reasons for this are somewhat complicated, so we'll study more about this later when we cover color expressions (Lesson 161).

Grammar Note:
None of these forms are used in the attributive form. Remember: polite forms don't modify nouns.

31. その冗談は面白くないです。
Sono jōdan wa omoshirokunai desu.
That joke is not funny.

32. 川は青くはないです。
Kawa wa aoku wa nai desu.
The river is not blue (but another color would describe the color better).

33. 信号は青くないです。
Shingō wa aokunai desu.
The light is not green.

34. あのリンゴは赤くありません。
Ano ringo wa akaku arimasen.
That apple is not red.

35. その答えは正しくないです。
Sono kotae wa tadashikunai desu.
That answer isn’t correct.

36 私は背が低くありません。
Watashi wa se ga hikuku arimasen.
I am not short.

Vocabulary Notes: 

①Amai 甘い may also mean "fragrant" and is generally also treated as the opposite of karai 辛い. The word may also be figuratively used to mean "tempting," "half-hearted," "naive," etc. 
②Kitanai 汚い may also mean "dirty" as in "indecent/vulgar" language as well as "underhanded."
③Okashii おかしい may also be used to mean "funny." 

Grammar Note:

The plain negative-past form may be used in both the attributive form and the predicative form. It is more common to see the negative-past in the attributive form when it is a part of a larger modifying, dependent clause. However, this is not a requirement. 

38. このパソコンは安くなかった。
Kono pasokon wa yasukunakatta.
This computer wasn’t cheap.

39. 給料は高くなかった。
Kyūryō wa takakunakatta.
The salary wasn’t/wages weren’t high.

40. その城は白くなかった。
Sono shiro wa shirokunakatta.
That castle wasn’t white.

41．葉っぱは茶色くなかった。
Happa wa chairokunakatta.
The leaves weren’t brown.

42. タイヤは黒くなかった。
Taiya wa kurokunakatta.
The tire(s) weren’t black.

43. 味はおかしくなかった。
Aji wa okashikunakatta.
The flavor wasn’t strange.

44. 今回はそこまで甘くはなかった。
Konkai wa soko made amaku wa nakatta.
This time it wasn't so sweet like that.

45. 天気はあまり良くなかった。
Tenki wa amari yokunakatta.
The weather wasn't that good.

46. この世は悪くなかった。
Kono yo wa warukunakatta.
This world wasn't bad.

47. 私の成績が悪かった理由
Watashi no seiseki ga warukatta riyū  
The reason why my grades were bad

Just as there were two methods to making an adjective negative in polite speech, there are also two methods to conjugating an adjective into negative past (was not) in polite speech.

The first method to create the negative-past involves simply involves attaching desu です to -kunakatta くなかった, giving -kunakatta desu くなかったです. This is proper in general conversation, but the second method is preferred in more careful speech.

The second (politer) method to create the negative-past is by utilizing the past tense form of arimasen ありません, which is arimasendeshita ありませんでした, producing -ku arimasendeshita くありませんでした.  This conjugation is very exceptional and doesn't follow typical verb conjugation norms. This is because the ん is a relic of older grammar, and so simply attaching でした which already has the past tense accounted for it was thought of as the best way to modernize the expression.