The verb observe has 9 senses (first 8 from tagged texts)
1. (41) detect, observe, find, discover, notice -- (discover or determine the existence, presence, or fact of; "She detected high levels of lead in her drinking water"; "We found traces of lead in the paint")
2. (17) note, observe, mention, remark -- (make mention of; "She observed that his presentation took up too much time"; "They noted that it was a fine day to go sailing")
3. (13) note, take note, observe -- (observe with care or pay close attention to; "Take note of this chemical reaction")
4. (10) observe -- (watch attentively; "Please observe the reaction of these two chemicals")
6. (3) observe, celebrate, keep -- (celebrate, as of holidays or rites; "Keep the commandments"; "celebrate Christmas"; "Observe Yom Kippur")
7. (2) watch, observe, follow, watch over, keep an eye on -- (follow with the eyes or the mind; "Keep an eye on the baby, please!"; "The world is watching Sarajevo"; "She followed the men with the binoculars")
8. (1) observe, keep, maintain -- (observe correctly or closely; "The pianist kept time with the metronome"; "keep count"; "I cannot keep track of all my employees")
9. observe, keep -- (conform one's action or practice to; "keep appointments"; "she never keeps her promises"; "We kept to the original conditions of the contract")