theory

The story

1. Proto-Hellenic*tʰā́wā
2. Ancient Greekθέᾱ (théā)
3. Proto-Indo-European*wer-
4. Proto-Indo-European*h₃ekʷ-
5. Proto-Indo-European*weyd-
6. Ancient Greekὁράω (horáō)
7. Ancient Greek*θεᾱ-(ϝ)ορός, *θεη-(ϝ)ορός (*theā-(w)orós, *theē-(w)orós)
8. Ancient Greekθεωρός (theōrós)
9. Ancient Greekθεωρία (theōría)
10. Late Latintheōria
11. Middle Frenchthéorie
12. English todaytheory

Borrowed from Middle French théorie, a learned borrowing from Late Latin theōria, borrowed from Ancient Greek θεωρία (theōría), from θεωρός (theōrós, “spectator”) + -ῐ́ᾱ (-ĭ́ā).

First known use, by meaning

• from 17th c. A coherent statement or set of ideas that explains observed facts or phenomena and correctly predicts new facts or phenomena not previously observed, or which sets out the laws and principles of something known or observed; a hypothesis confirmed by observation, experiment etc.
• from 17th c. The underlying principles or methods of a given technical skill, art etc., as opposed to its practice.
• from 18th c. A field of study attempting to exhaustively describe a particular class of constructs.
• 16th–18th c. Mental conception; reflection, consideration.
• from 18th c. A hypothesis or conjecture.