(physics) a radioactive substance that decays by emitting alpha particles

A stream of alpha particles.

(neurology) An electrical signal produced by the brain while the subject is relaxed.

The first and last; the beginning and end.

An exclamation denoting surprise.

(zoology, ethology) The dominant male in a group of animals. / (by extension) A dominant, assertive, protective, oftentimes successful, leadership-type man or male.

The science of finding, describing, classifying and naming living things.

(organic chemistry) A lactam having a three-membered ring structure.

(physics) A form of radioactivity in which alpha particles are emitted from the nucleus of an atom

(grammar) The prefix a- (or an- when prefixing a root which begins with a vowel) found in some English words of Greek derivation. It expresses negation or absence. The prefix has cognates in other Indo-European languages, including in- in Latin and un- in English.