Fall in love - When we fall in love with someone, we start to have very strong romantic feelings for that person. We use "in love" to mean that we are having very strong romantic feelings. And then if we combine it with the word "fall", it means that it's the beginning of this kind of relationship, or it's the beginning of these kinds of feelings.

Example sentences:
1. I think I'm falling in love.

2. Do you think he is falling in love with her?

3. They fell in love a long time ago.

Example dialogue: Two friends are talking about another friend's relationship.
A: I think Dave is falling in love with Susan.

B: Why do you say that?

A: Because he has been buying her flowers almost every day.

B: Yeah, that could be a sign he's falling in love.

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All out of love : If we fall out of love we are no longer in love with another person. We use this to describe when we lose romantic feelings for another person. We often fall out of love before we get a divorce or before we break up a relationship.

Example sentences:
1. I've fallen out of love with him.

2. She fell out of love.

3. They just fell out of love with each other.

Example dialogue: Two friends are discussing divorce.
A: Why did you and your ex-wife get divorced?

B: Well, I guess it was because we fell out of love with each other.

A: Why did you fall out of love?

B: I don't know. It is difficult to explain why people fall out of love.

Fonte: http://english1010.com/lesson_index.htm

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