After and At

After adjective - Being at or in the part of something opposite the front part.

At and after are semantically related. In some cases you can use "At" instead a preposition "After".

At noun - A highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thorium.

After and at are semantically related. Sometimes you can use "After" instead a preposition "At".