Except/Besides (除了)

除了 is a versatile word that can mean two nearly opposite things: "except for" (excluding) and "besides" (including). The key is what follows in the main clause.

When 除了 pairs with 都 (all), it means "except": 除了他以外，大家都来了 — "Except for him, everyone came." Here, 都 emphasizes that all others did something, and the person after 除了 is the exception.

When 除了 pairs with 也 or 还, it means "besides / in addition to": 除了英语以外，她还会说法语 — "Besides English, she can also speak French." Here, 还 adds something extra on top of what was mentioned.

以外 is optional and can be omitted in casual speech: 除了他，大家都来了 is perfectly fine. A useful test: if you can replace 除了 with "other than" and the sentence works in English, you have the right structure. Pay attention to 都 vs 也/还 — that is what determines the meaning.