Looking up...
To think carefully or deeply about something, often to make a decision or understand a concept.
Il réfléchit avant de répondre.
He thinks before answering.
Réfléchissez bien avant d'acheter cette maison.
Think carefully before buying this house.
The past participle 'réfléchi' can also be used as an adjective meaning 'thoughtful' or 'considered'.
'Réfléchir à' is the most common collocation, meaning 'to think about'.
Always use 'à' after 'réfléchir' when referring to the object of thought.
From Old French 'reflechir', from Latin 'reflectere' meaning 'to bend back' or 'to turn back'. The modern sense of 'to think' developed in the 16th century.
In French, 'réfléchir' is often used with the preposition 'à' to indicate the object of thought (e.g., 'réfléchir à un problème'). It can also be used reflexively ('se réfléchir') to mean 'to reflect' in the mirror.