forget or forget about?

You can forget about a lot of things, but you can forget less things.

Forget is a general word, forget about is more specific.

Generally speaking, both expressions are equivalent. The differences pop up in context. Forget about is used for properties of an item mostly, or an action with an item. Forget is to completely remove the item from "context".

For example,

• "I forgot my keys.": Person forgot their keys, as in it was left somewhere, and the person doesn't have it.
• "I forgot about my keys.": Person might have the keys, but forgot to Use it at the appropriate moment.
• "I want to forget about my keys.": Person would like to "un"know about its keys, or wants to bury the memories of it.
• "Forget about the keys!": Intent is to indicate that whoever it was addressed to won't get what the person asked for - right now, the keys.
• "Forget about it!": Not going to happen.

Take your forget a face example:

• "I forgot that face.": Person doesn't remember how someone's face looked like, like "I forgot how my Mom's face looks like.", when that person's mother might be dead, or unseen for a long time.
• "I forgot about that face.": Again, the didn't bring/didn't know/didn't use pattern. Or a more kind, non-direct way of saying one doesn't remember all the facial features - but not the entire face.

There can be different interpretations, but these are the general cases, i believe.

The semantic type of the direct object used after certain verbs is often restricted, and the sense of the verb involved may well vary with the object. This is also true when there is a preposition/particle involved. Here is a list of some of the possible semantic types of objects used with 'forget' and 'forget about':

• forget + possessions (eg I've forgotten my keys) = forget to bring / take etc them.
• forget + special occasion (eg I forgot her birthday) = forget about it and forget to mark it; implication of dire consequences
• forget + general activity (I forgot the time we went to Bristol) = forget to consider a relevant episode
• forget + image etc (eg I never forget a face / a picture I've painted / a piece of music I've heard / a horse I've ridden) = lose the ability to identify
• forget + knowledge (eg I forgot who scored / my lines) = lose the knowledge

whereas

• forget about + special occasion (I forgot about her birthday) = simply fail to remember (unmarked: no stress on failure to mark)
• forget about + general activity (I forgot about the time we went to Bristol) = forget to consider a relevant episode
• forget about + snippet of knowledge (I forgot about the Sadducees) = not bring to mind some relevant learning

The injunctions

• Forget it!
• Forget about it!

are interchangeable.

I can't help being overly literal: To forget is to lose a memory connection. This can be temporary or permanent, but not voluntary. If you 'forgot your keys', you forgot [to bring] your keys - if you actually forgot them, I could show them to you and you wouldn't know who they belonged to. To forget 'about' something is to lose relations that link to/from the object; you might forget that you used them last night, or that they were in the drawer.

I forgot the cat. (I can recall the cat, but I didn't bring it)

I forgot that the cat died. (I lost a specific connection) {note that a temporary loss is implied; otherwise you wouldn't know that you once knew that the cat died}

I forgot about the cat dying. (I lost unspecified connections [related to a specific event])