adjective 'frequent' describes something or someone that happens or appears often. It is used to indicate a high degree of frequency.
1. He is a frequent customer at the store.
2. I heard thunder several times in the last hour, leading me to believe that a storm is getting frequent.
3. She was a frequent visitor to the library.
frequent is often confused with often. Whereas, frequent refers to something happening or appearing over and over again, often simply means 'many times' and does not imply a repetitive process. Thus, it’s incorrect to say something like 'I often go to the gym,' since this does not indicate the frequency. 'Frequent' is always an adjective, while an adverb for this word should be 'frequently.'