隔週 and 毎週: alternate weeks and every week
Compare alternate-week meetings with weekly practice, separating the repeating week pattern from sessions per week and exact dates.
Leaving a week between scheduled weeks
隔週, read かくしゅう, means every other week. 隔週水曜日に集まります。 schedules meetings on alternate Wednesdays.
Check which week starts the pattern. 隔週 alone does not identify whether the current week is a meeting week.
Repeating in each week
毎週, read まいしゅう, means every week. 毎週水曜日に練習します。 says that practice takes place every Wednesday.
毎週二回練習します。 says that practice occurs twice each week. 毎週 alone does not fix the number of sessions at one per week.
Patterns, counts, and schedule changes
今月から隔週の授業を毎週に変更しました。 says that alternate-week lessons were changed to weekly lessons starting this month.
隔週でも、休みの週を変更する場合があります。 says that even an alternate-week schedule may have its off week changed. Check the individual timetable for actual dates.
Does 毎週二回練習します。 mean practicing twice on alternate weeks?
Show the answer and why
No. It means twice in each week. 隔週 would specify leaving a week between scheduled weeks.