Devotion, n.
Etymology: [F. dévotion, L. devotio.]
1. The act of devoting; consecration.
2. The state of being devoted; addiction; eager inclination; strong attachment love or affection; zeal; especially, feelings toward God appropriately expressed by acts of worship; devoutness. Genius animated by a fervent spirit of devotion. Macaulay.
3. Act of devotedness or devoutness; manifestation of strong attachment; act of worship; prayer. "The love of public devotion." Hooker.
4. Disposal; power of disposal. [Obs.] They are entirely at our devotion, and may be turned backward and forward, as we please. Godwin.
2 more senses
5. A thing consecrated; an object of devotion. [R.] Churches and altars, priests and all devotions, Tumbled together into rude chaos. Beau. & Fl. Days of devotion. See under Day.
Syn. -- Consecration; devoutness; religiousness; piety; attachment; devotedness; ardor; earnestness.
Shades of meaning
Fernald has no entry of its own for devotion; he lists it under allegiance, attachment, enthusiasm, friendship, love, religion.
Where he writes about it:
Affection expresses more warmth of feeling; we should not speak of a mother's attachment to her babe, but of her affection or of her devotion. — from attachment
Enthusiasm has now chiefly the meaning of an earnest and commendable devotion, an intense and eager interest. — from enthusiasm
Zeal is burning earnestness, always tending to vigorous action with all the devotion of enthusiasm, tho often without its hopefulness. — from enthusiasm
Friendship is always mutual; there may be unreciprocated affection or attachment, unrequited love, or even unrecognized and unappreciated devotion, but never unreciprocated or unrequited friendship; one may have friendly feelings toward an enemy, but while there is hostility or coldness on one side there can not be friendship between the two. — from friendship
Devotion, which in its fullest sense is self-consecration, is often used to denote an act of worship, especially prayer or adoration; as, he is engaged in his devotions. — from religion