Action and non-action(stative) verbs
Verbs which describe actions can be used in both continuous and non-continuous forms (see present simple or continuous):
She writes books. / She's writing a book.
He runs every day / He's running outside.
Your mother cooks very well / Your mother is cooking dinner.
Verbs which describe states, feelings, thoughts or opinions are not normally used with a continuous form.
The grandmother loves her grandchildren.
NOT:
The grandmother's loving her grandchildren.
He knows every person in the room.
NOT:
He's knowing every person in the room.
I want you to leave.
NOT:
I'm wanting you to leave.
She means what she's saying.
NOT:
She's meaning what she's saying.
Some common stative verbs are believe, belong, cost, depend, forget, hate, hear, know, like, love, matter, mean, need, prefer, realize, recognize, seem and suppose.
Wait! It's not that simple...
Some verbs can refer to states or actions, depending on the context.
I think it's a great movie. (in my opinion, it's a great movie)
I'm thinking of quitting my job. (I'm doing something(thinking) at the moment)
I have three children. ("I have" describes a state related to me)
I'm having lunch at the moment. (I'm doing something called having lunch)
Do you see any problems with that? (what's your opinion on that?)
I'm seeing two men approaching (seeing is an action I'm doing)
Other verbs like this include: agree, appear, doubt, feel, guess, hear, imagine, look, measure, remember, smell, weigh and wish.
The usage of stative verbs in the continuous form has many exceptional cases and it may be increasing in the English speaking world. Some common examples can be seen below:
I'm loving it. (not recommendable in formal contexts)
I've been meaning to call you.
Depending on the public's reaction, we may have to cancel the event.
It's costing me a fortune!
I'm relying on you.
While it's tempting to simply ignore the distinction between action and non-action verbs due to the number of exceptions, it's still helpful to avoid some common mistakes.