Every monday vs. Mondays: 有什么区别？

They are very similar and often interchangeable, especially at the B1 level. However, there's a subtle semantic difference for advanced learners. Every tends to view the items (Mondays) as a collective set, referring to all of them without exception. Each focuses more on the items as distinct individuals, one by one. For instance, Every student passed the exam emphasizes the group's success, while Each student received a certificate emphasizes individual recognition. In the context of recurring days, every Monday might feel slightly more encompassing of the entire series, while each Monday could highlight the individual instance more intensely. For most practical purposes at this CEFR level, treat them as synonyms when referring to repeated days.

For events occurring every two weeks, or every other week, you cannot simply use the plural day form. You must be more specific. Common expressions include:

• every other Monday (or every second Monday)
• every two weeks on a Monday
• bi-weekly on Mondays (though bi-weekly can sometimes be ambiguous, meaning twice a week or every two weeks, so every other Monday is often clearer)

Yes, the same underlying principle largely applies to other recurring time units. You can observe similar patterns:

• every week (e.g., I go home every week.) vs. weeks (e.g., Weeks seem to fly by quickly.)
• every month (e.g., The rent is due every month.) vs. months (e.g., Months of hard work finally paid off.)
• every summer (e.g., We visit the beach every summer.) vs. summers (e.g., Summers in the city are truly magical.)

Generally, yes, on Mondays is perceived as slightly more formal or complete. Omitting on is very common in informal conversation, particularly in American English, and in digital communication like texting or social media posts. In formal academic or business writing, or when you want to avoid any ambiguity, including on is often the safer and more traditionally correct choice. Both are grammatically acceptable for expressing recurring actions, but the presence of on adds a touch more formality.

In this case, you must use the singular form with the preposition on. For example:

• The project deadline is on Monday. (Referring to the upcoming Monday)
• Are you free on Tuesday next week? (Referring to a specific Tuesday)

When in doubt, consider your emphasis:

• Choose every [day] if you want to stress absolute, unbroken consistency, or a strict schedule. It leaves no room for missed occurrences or exceptions in the pattern. This form is often clearer for precise scheduling.
• Choose [days] (or on [days]) if you are describing a general routine, a habitual activity, or the typical characteristics of that day. This form is more conversational and allows for a slightly looser interpretation of regularity, though it still implies a strong pattern.