This lesson is about how you can get adverbs out of any adjective in Japanese. It'll be easy!
To make an adjective an adverb, you use the 連用形. All this term means is that it shows a continuation of a phrase, and because adverbs are extensions of a verb phrase, the term makes a lot of sense. We have two classes of adjectives, so they still look different when turned into adverbs.
The 連用形 of 形容詞 ends in く. So, all you do is drop い and add く. For 形容動詞, we have use the 連用形 に*. These adverbs are normally translated with "-ly". However, for whenever English is weird and doesn't let us use -ly, we have to go with another translation.
To easily explain.
To spend the holidays merrily.
To cut something into small pieces.
I study in my own room quietly every day.
The washbasin was dyed blue with indigo.
That light over there shined red.
Phrase Note: あの is literally translated in English as "that over there" as it refers to something not directly near the speaker or listener. However, when the object of reference is truly literally "over there" as in on the other side of the speaker and listener, あの向こうの is more appropriate.
My older sister became nice.
1. When we want to say that something "becomes X" but X is actually an adjectival attribute, we turn the adjective into an adverb and then add なる. So, "to become red" is 赤くなる. 赤くになる is wrong. However, you say きれいになる for "to become pretty". Remember that there are two classes of adjectives and that they always conjugate differently.
2. Continuing on 2, 信号が青くなった actually means "the light turned green". 青, not 緑, is the color used for streetlights for "green".
Please be more quiet
Grammar Note: The opposite of "(adjectival) adverb + なる" is "(Adjectival) adverb + する", which means "to make..." as in implementing a change.
The sun sets early in the winter.
To take a deep breath.
確か VS 確かに
確か means "certain", but as an adverb, it's often paired with だろう・でしょう to mean "if I'm not mistaken". The other adverb form 確かに means "certainly". So, they're slightly different.
The population of the world, if I'm not mistaken is around 7 billion people.
The tree will certainly fall.
13a. 確か（か）? (Very casual and a little blunt)
Is that for certain?
That is not definitive evidence.
Nuance Note: 多分 is less certain than 確か and きっと is more certain than 確かに.
Not all adverb phrases will be made similarly. For example, 必要に is not used. "Necessarily" is instead 必ず. Another example is けっこう. Although it too is a 形容動詞, it's adverbial form is just けっこう. Lastly, we have 少しく meaning "just a little". The word comes from when 少し was an adjective. It is occasionally used in the written language.
Today is quite cold.
To state a little bit of what you think.
Ends in に but not from 形容詞
Even though an adverb may end in に, this doesn't mean it necessarily comes from an adjective. Though this is usually the case, there are still very commonly used exceptions to this.
There are no problems present right now.
(I/we) immediately left the airport in a rental car.