Learn English – Difference between “mandatory” and “indispensable”

I think they're all pretty much interchangeable. As I tried to think of an exception, I wondered if throw would be a bit more appropriate for a wild party, and less appropriate for a less festive occasion. However, I found plenty of instances of "throw an office party" on Google, enough to convince me that throw doesn't necessarily imply "wild and crazy."

One additional verb you could use is "host": We are going to host a party on the 11th.

For what it's worth, here's an Ngram, but there's nothing too remarkable there.

It does depend on the context, but let's imagine that a group of people are discussing a collision on the roads.

"I believe it could have been prevented."

To me, and I'm not sure if the implications vary between individuals, but the speaker is saying that something could have been done a while before the situation occurred. For example, it may have been avoided by:

• Safer road laws
• A lower speed limit
• Better brakes on cars

On the other hand, "avoided" implies that the actions taken to circumnavigate the incident would have been last minute, or unplanned.

• Braking
• Veering out of the way
• Honking the drivers' horns

Google defines the terms as:

Avoid: keep away from or stop oneself from doing (something).

Prevent: keep (something) from happening.

They could be used as synonyms, and are fairly interchangeable (although one usually feels more natural to speak.)