adverb
moderately; just right; properly
Describes doing something to a moderate, appropriate degree—not too much, not too little. Often used when the result is pleasantly balanced or suitable.
スープに塩を程よく加える。
Add salt to the soup moderately.
彼は程よく距離を置いて接してくれる。
He keeps a comfortable distance when interacting with me.
適度に also means 'moderately' but is more formal and often used in objective descriptions, while 程よく carries a nuance of subjective appropriateness and pleasant balance.
ちょうどよく means 'just right' or 'perfectly', emphasizing exact suitability, whereas 程よく implies a moderate degree that is pleasantly balanced.
Compound of 程 (ほど, 'extent, degree') + adverbial form of 良い (よい, 'good'). Literally 'to a good extent'.