dy·ad (dīăd′, -əd)
1. Two individuals or units regarded as a pair: the mother-daughter dyad.
2. Biology One pair of homologous chromosomes resulting from the division of a tetrad during meiosis.
a. A function that draws a correspondence from any vector u to the vector (v·u)w and is denoted vw, where v and w are a fixed pair of vectors and v·u is the scalar product of v and u. For example, if v = (2,3,1), w = (0,-1,4), and u = (a,b,c), then the dyad vw draws a correspondence from u to (2a + 3b + c)w.
b. A tensor formed from a vector in a vector space and a linear functional on that vector space.
Made up of two units.
[From Greek duas, duad-, from duo, two; see dwo- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.