Definition of variability :
1. The power possessed by living organisms, both animal and vegetable, of adapting themselves to modifications or changes in their environment, thus possibly giving rise to ultimate variation of structure or function.
2. The quality or state of being variable; variableness.
irregularity (part of speech: noun)
- The song sparrow shows a high degree of variability both in its song and in its nesting- habits, each bird having several songs of its own, while one may nest upon the ground and another in a low bush, or in the vines on the side of your house. - "Ways of Nature", John Burroughs.
- Round the edges of each of these were little irregular rainbow- coloured halos of their own interrupting and variegating the continuous bands of the corona; while throughout all was discernible a perpetual variability, like the flashing or shooting of colour in the opal, the mother- of- pearl, or similarly tinted translucent substances when exposed to the irregular play of bright light- only that in this case the tints were incomparably more brilliant, the change more striking, if not more rapid. - "Across the Zodiac", Percy Greg.
- Having in the preceding pages touched upon the subject of insect variability, as the occasional result, to a greater or less extent, of climatal and other influences; let us now proceed to consider the importance of a certain physical condition, which will be found, I believe, on inquiry, to be accompanied by a more decided modifying power than any which we have yet discussed. - "On the Variation of Species, with Especial Reference to the Insecta ; Followed by an Inquiry into the Nature of Genera", Thomas Vernon Wollaston.