At the end of the ME Period the declensions of the Adjective disappeared and there was a necessity to find another way to indicate the definiteness/indefinite ness of a noun. Thus the articles appeared.In OE the word-order was free because inflections were employed to show the relations of the words in a sentence.
In ME and NE the majority of the inflections disappeared and the word-order became fixed. This meant that the first place in a sentence was usually occupied by the theme (information already known marked with the definite article) and the second place – by the rheme (new information marked with the indefinite article).Definite Article. As it was mentioned above, the definite article appeared from the OE demonstrative pronoun se (M, Sg, Nom) from the paradigm of the
OE demonstrative pronoun “that” because it was often used to indicate a definite object or notion.Indefinite Article. The indefinite article appeared from the OE numeral ān (one) and had the meaning of “oneness” (it still indicates only nouns in Sg, i.e. nouns indicating one object or notion).In OE ān had 5-case paradigm that was lost in ME and only one form was left – oon/one. Later it was employed in the building of the indefinite article a/an.The indefinite article may have been used more often as an, especially in the early centuries of Middle English, because it reflects the original spelling and the words shared roots with the number one.
Other spellings of it could include on, ane, anne, en, enne, and ene. The definite article had other forms including de, þeo, te, þea, þie, and the contracted form th'. the definite articles in the The English definite article the, written þe in Middle English,