This is the 3501st most frequent Japanese word.
細
"細" means "small," "fine," or "detailed" in English.
Here, '細かいこと' (細かい事) means 'details' or 'minute things.' '細' is used in the adjective '細かい,' referring to something of small granularity or intricacy.
細かいことに気を配る必要があります。
You need to pay attention to details.
In this sentence, '細い' is the adjective form of '細,' meaning 'narrow' or 'slender.' It describes the path as being narrow in width.
彼は細い道を通り抜けた。
He passed through a narrow path.
Here, '細い' again describes something slender or thin, applied to the 'line' ('線'). It conveys the physical thinness of the line.