an adverb is a part of speech that modifies or describes a verb, adjective, other adverb, phrase, clause, or sentence. They typically answer questions like 'how?', 'when?', 'where?', and 'how much?' When used as an adverb, 'barely' means 'only just; almost not'.
when used as an adverb in its most basic form, 'barely' is used to express a nearly negative statement or description about the degree or extent of something, emphasizing that it was only just barely true or that it came close to not being true. This usage could imply either success or failure, depending on the context. It must always be placed directly before the word that it is modifying.
1. I barely made the train in time; I had to sprint to catch it.
2. I was so exhausted that I could barely walk.
3. He barely passed the test, though it took him several attempts.
'barely' should always be used to describe a nearly negative judgement or outcome--a slight success or a near miss. For example 'I barely passed the test' means that the speaker only just managed to pass the test, but 'I barely failed the test' means that the speaker almost passed. It should never be used to describe overly enthusiastic outcomes, such as 'I barely achieved an A'.