triplet
A three-base codon of the genetic code. Also a component of the mitotic spindle, seen in crosssection as one of nine structures, each composed of a microtubule doublet with an additional series of protofilaments that constitute a third subunit; the nine triplets radiate from a central axis and appear as a cartwheel.
[О. С. Воеводина Англо-русско-немецкий словарь биотехнологических терминов с определениями.]