The weak forms are used:
(1) after the definite article:—se æþela cyning (the noble king); þæs æþelan cyninges, þæt gōde męregrot, þā gōdan męregrotu.
(2) after þis:—þās earman landlēode (these poor people, pl.); þes hālga cyning (this holy king), þisses hālgan cyninges.
(3) occasionally after other demonstrative and indefinite adjectives, and often after possessive pronouns:—þīne dīeglan gold-hordas (thy hidden treasures).
(4) in the vocative:—þū yfla þēow and slāwa! (thou bad and slothful servant); ēalā þū lēofa cyning! (oh, thou dear king).
Note that ōþer always keeps the strong form: þā ōþru dēor (the other wild beasts). So also do the possessive pronouns:
þās mīn word (these my words). Ān in the sense of 'one' keeps the strong form to distinguish it from the weak āna = 'alone': þæt ān dēorwierþe męregrot (the one precious pearl).
ARTICLES.
The definite article is omitted as in Modern English before names such as God, and also before Dryhten (the Lord), Dēofol (the Devil), although se Dēofol also occurs, and names of nations:—Bretta cyning (king of the Britons).
It is omitted in many prepositional combinations, not only in those where it is omitted in Modern English also, as in siġefæst on sǣ and on lande (victorious on sea and on land), but also in many others: ġewęnde tō wuda on·ġēan (went back to the wood); se flothęre fērde eft tō sċipe (the army of pirates went back to their ships); hē fēng tō rīċe (he took the government—came to the throne).