動詞 define:

1. give a definition for the meaning of a word
2. determine the essential quality of
   同義詞：specify, delineate, delimit, delimitate
3. determine the nature of
4. show the form or outline of
   同義詞：delineate

1. Definitions should not be more difficult to understand than the words they define.
   詞語的定義不應比所解釋的詞語更難理解。
2. When boundaries between countries are not clearly defined, there is usually trouble.
   國與國之間的邊界未明確劃定時，通常會發(fā)生糾紛。
3. The powers of a judge are defined by law.
   法官的權限是由法律規(guī)定的。

de.fine

v.（動詞）
de.fined,de.fin.ing,de.fines
v.tr.（及物動詞）

To state the precise meaning of (a word or sense of a word, for example).
給…下定義：給（例如，單詞或詞義）下精確的定義
To describe the nature or basic qualities of; explain:
闡釋：描述…的性質或基本特征；解釋：
例句：
define the properties of a new drug; a study that defines people according to their median incomes.
解釋一種新藥的特性；根據人們的平均收入闡釋的調查

To delineate the outline or form of:
勾畫出…的輪廓或外形：
例句：
gentle hills that were defined against the sky.
在天空的襯托下顯得輪廓分明的丘陵

To specify distinctly:
清楚地規(guī)定：
例句：
define the weapons to be used in limited warfare.
明確地規(guī)定只能用于局部戰(zhàn)爭中的武器

To serve to distinguish; characterize:
用于分辨；顯示…的特色：
例句：
.portraits that defined the style of an epoch.(Gloria Vanderbilt)
.表現一個時代風格特征的描寫.(格洛麗亞·范德比爾特)

v.intr.（不及物動詞）
To make or write a definition.
下定義

來源：
Middle English definen, diffinen
中古英語 definen, diffinen
from Old French definir, diffiner
源自 古法語 definir, diffiner
from Latin dôfonore [to limit, determine]
源自 拉丁語 dôfonore [限定，確定]
dô- [intensive pref.] * see de-
dô- [加強語意的前綴] *參見 de-
fonis [boundary, limit]
fonis [邊界，界線]

【引伸】
defin.abil.ity
n.（名詞）
defin.able
adj.（形容詞）
defin.ably
adv.（副詞）
define.ment
n.（名詞）
defin.er
n.（名詞）