Which preposition should I use here: "thinking of" or "thinking about"?

'Thinking of' usually means 'considering'. 'I'm thinking of a new car' would mean considering replacing your current model, whereas 'thinking about a new car' is what you do when watching the adverts, without necessarily planning to buy one. (So 'thinking about getting a new keyboard' would involve "Well, typing would be faster, but it's another cable to tangle, and it costs a bit, and..."). But it's only a connotation, not a meaning, and don't try to apply it to your sweetheart!

I think about my life and i am thinking of my life. The second one can not be in simple present form . So i think the first one means you think about all moments of your life but the second one carrues a contemoray thought

As a language teacher, this is something my students ask me a lot. So, I have researched this topic the best way I could, which is by using Corpora (an analysis of millions of texts in English). I did this in order to give the best answer I possibly could, because being a native speaker was not enough to put everything in order. Here's what I found.

Compared to the previous posters, some of what is said is true and other is not. So both of these are actually equally frequent in their use, around 80,000. Mostly, these have very different meanings, except one case, which is giving an opinion (see below). The frequency of this use case, however, is not so high ("what do you think about/of"+"what you think about/of" is 4-5% of total use cases.

Summary:

Think of (Meaning: bring something into your mind) Use cases: • New ideas • Reminder of people or things • Brainstorming • Finding solutions • Giving an opinion (About 5% of total use cases)

Think about (Meaning: concentrate and focus on something) Use cases: • Concentrating on a topic, person or action • Taking a person into consideration • Memories and experiences • Giving an opinion (About 4% of total use cases)

Common phrasing:

“Think of someone who helped you.” = Search through your memories.

“California is an agricultural state and so many people don't even think of it that way.” = Consider something as something, an opinion.

“And that's a funny thing, when you come to think of it.” – when it enters your mind.

“What do you think of her?” = Invitation to give an opinion

“Think about it. It’s a great idea.” = Give it consideration and contemplation.

“I want you to think about your daughter who loves you before you make this decision.” = Keep her in consideration.

“You're not a kid anymore. You have to think about your future, Jess.” = Keep it in consideration.

“What do you think about that?” = Invitation to give an opinion

The chosen answer in this case gives this example of equal meaning: "When I think about/think of my mother, who passed away three years ago, I get very sad."

1. These sentences have the potential to be equal in meaning but only when combined in this way. Here's the difference: "When I think of my mother..." = When I am reminded of my mother. In this case, just the though makes me sad. For example, seeing a picture or her favourite TV show, could make make me think of her, and that makes me sad. "When I think about my mother..." = When I concentrate on and contemplate her. In this case, the contemplation and concentration on the topic makes me sad. Just being reminded of her doesn't affect me so much, but really concentrating on the topic does. Just seeing her picture or just seeing her favourite things, wouldn't make me sad. But when I sit and think about her and the time we spent together, it does.

Be careful when analyzing sentences outside their context to determine meaning. The meaning although close, is not the same and clearly implies or requires a different context.

Conclusion

In the majority of cases, (95%) these two have different meaning. It is only when giving opinions that they can be used interchangeably. In some cases, it is easy to see the difference and in some specific situations, if you ignore the context, it is not so easy. Have a look at the summary and the examples in order to see when one should be used versus the other.

For more information have a look at https://www.english-corpora.org/coca/