深い（ふかい、fukai）
- deep

The Japanese word 深い (fukai) primarily means "deep." It can describe depth in various contexts, including physical depth, emotional depth, or the profundity of a subject. The meaning shifts slightly depending on the noun it modifies. The word 深い can also imply intensity or seriousness.

⚫︎ 海が深い Translation: The sea is deep. ⚫︎ 深い悲しみ Translation: Deep sorrow. ⚫︎ 彼の知識は深い Translation: His knowledge is profound.

You can use 深い to describe the physical depth of water, a hole, or a forest. It can also describe abstract concepts like feelings, understanding, or thought. Consider the context to grasp its nuanced meaning. It can be used in both formal and informal conversations.

The word is typically written as 深い in kanji, but it can also be written in hiragana as ふかい. The okurigana (the suffix hiragana) is always "い" (i).

⚫︎ 濃い (koi): This can sometimes be used in a related sense (e.g., in the context of a "deep" color or flavor), but the core meaning is "thick" or "intense." ⚫︎ 奥深い (okushibukai): This means "profound" or "deep" in a more abstract way. ⚫︎ 重大 (juudai): meaning "serious" or "important". It can be used for deep meaning.

⚫︎ 浅い (asai): This means "shallow."

この川は深いので、注意してください。 ・Translation: Be careful, this river is deep. ・Explanation: This sentence uses 深い to describe the physical depth of a river, warning the listener to be cautious.

その映画はテーマが深い。 ・Translation: That movie has a deep theme. ・Explanation: Here, 深い refers to the thematic complexity or profundity of the movie.

The etymology of 深い is not definitively known, but it is believed to be derived from the verb stem of "深(ふか)める" (fukameru), which means "to deepen," with the "い" (i) ending making it an adjective.