A prefix meaning 'every' or 'each', used before nouns/time expressions (e.g., 毎朝 = every morning).
毎朝、コーヒーを一杯飲みます。
I drink a cup of coffee every morning.
この店は毎週月曜日が休みです。
This shop is closed every Monday.
大会は毎年九月に行われる。
The tournament is held every September.