Demi- \Dem"i-\ [F. demi-, fr. L. dimidius half; di- = dis- + medius middle. See Medium, and cf. Demy, Dimidiate.]

A prefix, signifying half.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Demi \De*mi"\, n. See Demy, n.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Demy \De*my"\, n.; pl. Demies. [See Demi-.]

1. A printing and a writing paper of particular sizes. See under Paper.

2. A half fellow at Magdalen College, Oxford. [Written also demi.]

He was elected into Magdalen College as a demy; a term by which that society denominates those elsewhere called ``scholars,'' young men who partake of the founder's benefaction, and succeed in their order to vacant fellowships. --Johnson.

Source: Webster's Revised Unabridged Dictionary (1913)