Obs. Forms: 1–2 þy, 2–3 þi. [OE. ðý, þý, instrumental case of demonst. and relative pron. se, séo, þæt: see THAT, and cf. THE adv.]
1. a. orig. By means or by reason of that, because of that, therefore. b. In relative sense: For the reason that, because.
c. 897. K. Ælfred, Gregory’s Past. C., xxviii. 192. Ðy him is micel ðearf, ðonne he tela lærð, ðæt he eac tela do.
c. 1000. Sax. Leechd., II. 86. Smire mid huniʓ, þæt þy þe raþor sio hryfing of fealle.
c. 1175. Lamb. Hom., 93. Þi bileafden heo heore timbrunge.
c. 1200. Trin. Coll. Hom., 205. Wilfulshipe and lichamliche lustes and liðere lahtres, þi ne mai no man gode folȝen.
a. 1250. Owl & Night., 860. Ich rede þi þat men beo ware.
c. 1275. Woman of Samaria, 39, in O. E. Misc., 85. Ich wot … Þat þu me hauest soþ iseyd … Þi of one þinge sey me iredynesse.
c. Hence in for thy, for that reason, therefore: see FOR-THY; also in OE. mid þý, with that, seeing that, since, when, while; to þý, to that end or purpose, therefore.
2. Preceding an adj. or adv. in the comparative degree: see THE adv.
