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. traveler, traveller - a person who changes location. AWOL - one who is away or absent without leave. defaulter - someone who fails to make a required appearance in court. exile, expat, expatriate - a person who is voluntarily absent from home or country; American expatriates. hooky player, truant - one who is absent from school without permission.