Relating to or characteristic of summer; occurring during the summer season.
From Latin 'aestivus' meaning 'of or belonging to summer,' derived from 'aestas' (summer). The English adjective maintains the original sense of the Latin root.
This is an old-fashioned but poetic way to describe summer things—you might hear it in historical botanical texts describing 'aestive flowers' that bloom only when it's hot.
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