The Beginning of Romantic Feelings in Psychology

After you have a special feelings towards someone,
you start feeling irritated or upset because of them.

In the field of psychology, those feelings are defined as a “fancy”,
which means you are in love with the person.

I'm not sure whether this makes sense or not though.

To only be attracted or have special feelings for someone 

does not seem like enough to be called “fancy”.

I know American people rarely use the word "fancy", 

but I can't find the suitable word. I meant it 恋 or 恋愛感情 ,not love, in Japanese.