Any of a group of organic compounds having two fused six-member rings each containing two nitrogen atoms and four carbon atoms. One of the rings is a pyrimidine, the other a pyrazine. Pteridines include folic acid and the pigments of butterfly wings.
1. a combining form meaning “fern,” used in the formation of compound words: pteridology.
noun 1. the branch of botany dealing with ferns and related plants, as the horsetails and club mosses. noun 1. the branch of botany concerned with the study of ferns and related plants
[tuh-rid-uh-fahyt, ter-i-doh-] /təˈrɪd əˌfaɪt, ˈtɛr ɪ doʊ-/ noun 1. any plant of the division Pteridophyta, characterized by vascular tissue and differentiation into root, stem, and leaves, comprising the ferns, horsetails, and club mosses. pteridophyte /ˈtɛrɪdəʊˌfaɪt/ noun 1. (in traditional classification) any plant of the division Pteridophyta, reproducing by spores and having vascular tissue, roots, stems, […]
[tuh-rid-uh-spurm, ter-i-doh-] /təˈrɪd əˌspɜrm, ˈtɛr ɪ doʊ-/ noun 1. seed fern. pteridosperm /ˈtɛrɪdəˌspɜːm/ noun 1. any extinct seed-producing fernlike plant of the group Pteridospermae Also called seed fern
noun, Craniometry. 1. the craniometric point at the side of the sphenoidal fontanelle. pterion pter·i·on (těr’ē-ŏn’, tēr’-) n. The junction of the greater wing of the sphenoid bone and the squamous temporal, the frontal, and the parietal bones.