A good dictionary is the handmaid of the linguist. 一部好字典封语言学家的帮助甚大。
handmaid
[ noun ]
in a subordinate position
<noun.state> theology should be the handmaiden of ethics the state cannot be a servant of the church
a personal maid or female attendant
<noun.person>
Handmaid \Hand"maid`\ (h[a^]nd"m[=a]d`), Handmaiden \Hand"maid`en\ (h[a^]nd"m[=a]d`'n), n. A maid that waits at hand; a female servant or attendant. [WordNet sense 2]
2. Something or someone serving in a subordinate position; as, theology should be the handmaiden of ethics. [WordNet sense 1]