1. Watch attentively
   "Please observe the reaction of these two chemicals"
    
2. Pay close attention
   "The scientist observed the reaction carefully";
   - note, take note
    
3. Determine the existence, presence, or fact of
   "Scientists observed a new particle";
   - detect, find, discover, notice
    
4. Speak of something; say to bring other people's attention to something
   "She observed that his presentation took up too much time";
   - note, mention, remark
    
5. See and monitor someone or something
   "The world is observing Sarajevo";
   - watch, follow, watch over, keep an eye on
    
6. Show respect towards
   "We should observe our elders";
   - respect, honor [US], honour [Brit, Cdn], abide by
    
7. Behave as expected during holidays or rites
   "Observe Yom Kippur";
   - celebrate, keep
    
8. Stick to correctly or closely
   "The pianist observed time with the metronome";
   - keep, maintain
    
9. Conform one's action or practice to
   "observe appointments";
   - keep

Derived forms: observed, observing, observes

Type of: abide by, accept, acquit, act, bear, behave, carry, check, check into, check out, check over, check up on, comply, comport, conduct, deport, descry [literary], do, espy, follow, go over, look into, look on, say, sight, spot, spy, state, stick to, stick with, sus [Brit, informal], suss [Brit, informal], suss out [Brit, informal], tell, watch

Antonym: disrespect, offend

Encyclopedia: Observe