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.
Definition of PRESENT. 1. a obsolete: present occasion or affair b plural: the present words or statements; specifically: the legal instrument or other writing in which these words are used. 2. a: the present tense of a language b: a verb form in the present tense.