Definition of photoperiodicity in US English:

photoperiodicity

noun

  • Photoperiodism. Also: the regular cycle of changes in day length to which photoperiodism is a response.

Origin

1920s; earliest use found in Ecology. From photoperiodic + -ity; compare -icity.

Pronunciation

photoperiodicity

/ˌfəʊtə(ʊ)pɪərɪəˈdɪsɪti/