• 毎日まいにち — every day
• 毎週まいしゅう — every week
• 毎年まいとし — every year
• 毎朝まいあさ — every morning
• 毎晩まいばん — every night
• 毎回まいかい — every time
• 日毎ひごと — day by day

毎 is historically related to 母 (mother) in its shape. In older forms, 毎 looks like 母 with a small extra mark added, and the character came to express repetition and regularity — the idea of something happening “every time.” That makes it a good match for words like 毎日 (every day) and 毎回 (every time).