de·cline 
(dĭ-klīn)
(dĭ-klīn)v. de·clined, de·clin·ing, de·clines
v.intr.
1. To express polite refusal: I wanted to invite them but I was afraid they would decline.
2.
a. To slope downward; descend: The roof declines at a steep angle.
b. To bend downward; droop: boughs declining toward the ground.
3. To degrade or lower oneself; stoop: refused to decline to their level of behavior.
4. To deteriorate gradually; fail: His health has been declining for years.
5.
a. To sink, as the setting sun.
b. To draw to a gradual close: We made our way home as the day declined.
v.tr.
1. To refuse politely: I declined their offer of help. See Synonyms at refuse1.
2. To cause to slope or bend downward.
3. Grammar To inflect (a noun, a pronoun, or an adjective) for number and case.
n.
1. The process or result of declining, especially:
a. A gradual deterioration, as in numbers, activity, or quality: "overwhelming evidence that fish stocks ... are in decline" (Jonathan Bocknek).
b. A downward movement or fall, as in price.
c. A deterioration of health: the patient's rapid decline.
2. A downward slope; a declivity: the sharp decline of the dunes to the sea.
[Middle English declinen, from Old French decliner, from Latin dēclīnāre, to turn away, bend downward, change the form of a word : dē-, de- + -clīnāre, to lean, bend; see klei- in the Appendix of Indo-European roots.]
de·clina·ble adj.
de·cliner n.