Triplet
One of three, as: <B>1.</B> One of three babies in a multiple birth.
Or three animals gestated together.
<B>2.</B> In genetics, a set of three bases in DNA.
Also called a codon.
See: Crick-Brenner experiment.
<B>3.</B> In optics, a combination of three simple lenses cemented together.<BR><BR>The word triplet came into use in the mid-17th century.
It was formed from triple, just as doublet was formed from double