observe
verb
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”
make mention of
“She observed that his presentation took up too much time”
“They noted that it was a fine day to go sailing”
observe with care or pay close attention to
“Take note of this chemical reaction”
watch attentively
“Please observe the reaction of these two chemicals”
show respect towards
“honor your parents!”
behave as expected during of holidays or rites
“Keep the commandments”
“celebrate Christmas”
follow with the eyes or the mind
“Keep an eye on the baby, please!”
“The world is watching Sarajevo”
stick to correctly or closely
“The pianist kept time with the metronome”
“keep count”
conform one's action or practice to
“keep appointments”
“she never keeps her promises”
Synonymskeep
Source: WordNet 3.1, Princeton University