At and By

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

By is a synonym for at in position topic. In some cases you can use "By" instead the word "At" as a preposition or an adverb, when it comes to topics like about. popular alternative

By preposition - Close to.

At is a synonym for by in position topic. You can use "At" instead the word "By" as a preposition or an adverb, if it concerns topics such as no later than. popular alternative