"Trepidation" is when you are fearful about doing something. "Phobia" is when you are always fearful about the same thing. "Cowardice" is when you are always fearful of many things. "Angst" is when you are fearful due to your place in life or the cosmos. "Anxiety" is a general, active feeling of fear. Having "jitters", "the creeps", "uneasiness", or "dread" means you are currently feeling afraid something will happen. If some frightening event just happened, you have "terror", "horror", "panic", or "had a scare". "Misgiving" means you do not feel completely good about something. All of these words are fairly common. The thesaurus will show many more, but they don't all necessarily involve some very clear idea of fear. I think these do.

a noun that could be used as synonyms of 'fear' - 'dread' (this is quite a strong fear); phobia - this is a very strong and irrational fear of something. However neither of these would be used commonly in everyday conversation (unless in fact you wanted to indicate that the person had an abnormally severe fear of something). I don't think we have a word for 'a mild fear'! Perhaps aversion comes close - it is not quite the same as fear though. BTW, we say 'a fear of....'; 'an aversion to...........'

Hi. So you want to use a synonym of fear for common conversation? If something is a minor issue, people might say, "I'm afraid," or perhaps "I'm worried." If the topic is more major, it is common to say, "I'm terrified," or "I'm frightened." Hope this is of help. :)