Atoms of the same element that have different masses are called isotopes. Different masses result when there are different numbers of neutrons. All atoms of a particular element have the same number...
Definition of absent. 1 : not present at a usual or expected place : missing was absent from class today sharing memories of absent friends She was conspicously absent [=her absence was very noticeable] at the meeting. absently. adverb He replied absently to her question. Examples of absent in a sentence.
absentee - one that is absent or not in residence. air traveler, air traveller - someone who travels by airplane. arriver, comer, arrival - someone who arrives (or has arrived) astronaut, cosmonaut, spaceman - a person trained to travel in a spacecraft; the Russians called their astronauts cosmonauts.