observe

v. watch, study; monitor, supervise; discern; keep, honour; fulfill religious commandments; follow, abide by; remark, comment

Observation is an activity of a sapient or sentient living being (e.g. humans), which senses and assimilates the knowledge of a phenomenon in its framework of previous knowledge and ideas. Observation is more than the bare act of observing: To perform observation, a being must observe and seek to add to its knowledge. Observations are statements which are determined by using one of the five senses. Observations aroused by self-defining instruments are often unreliable­¹. Such observations are hard to reproduce because they may vary even with respect to the same stimuli. Therefore they are not of much use in exact sciences like physics which require instruments which do not define themselves. It is therefore often necessary to use various engineered instruments like: spectrometers, oscilloscopes, cameras, telescopes, interferometers, tape recorders, thermometers etc. and tools like clocks, scale that help in improving the accuracy,  quality and utility of the information obtained from an observation. Invariable observation requires uniformity of responses to a given stimulus, and devices promoting such observation must not give out rebellious output as if having "a mind (or opinion) of their own". In statistics, an observation, whether of a sample or the population, measures one or more properties (weight, location, etc.) of an observable entity enumerated to distinguish objects or individuals.
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Verb
1. 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"
(synonym) detect, find, discover, notice
(hypernym) sight
(hyponym) find out, catch out
(verb-group) discover, find
(derivation) perceiver, observer, beholder
2. make mention of; "She observed that his presentation took up too much time"; "They noted that it was a fine day to go sailing"
(synonym) note, mention, remark
(hypernym) state, say, tell
(hyponym) comment, notice, remark, point out
(derivation) observer, commentator
3. observe with care or pay close attention to; "Take note of this chemical reaction"
(synonym) note, take note
(entail) perceive, comprehend
(derivation) perceiver, observer, beholder
4. watch attentively; "Please observe the reaction of these two chemicals"
(hypernym) watch
(hyponym) bird, birdwatch
(derivation) observation, reflection, reflexion
5. show respect towards; "honor your parents!"
(synonym) respect, honor, honour, abide by
(hypernym) accept
(hyponym) lionize, lionise, celebrate
6. celebrate, as of holidays or rites; "Keep the commandments"; "celebrate Christmas"; "Observe Yom Kippur"
(synonym) celebrate, keep
(hyponym) commemorate, mark
(derivation) ceremony, ceremonial, ceremonial occasion, observance
7. 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"
(synonym) watch, follow, watch over, keep an eye on
(hypernym) check, check up on, look into, check out, suss out, check over, go over, check into
(hyponym) keep tabs on
(verb-group) trace, follow
(derivation) perceiver, observer, beholder
8. observe correctly or closely; "The pianist kept time with the metronome"; "keep count"; "I cannot keep track of all my employees"
(synonym) keep, maintain
(derivation) observation, reflection, reflexion
9. conform one's action or practice to; "keep appointments"; "she never keeps her promises"; "We kept to the original conditions of the contract"
(synonym) keep
(hyponym) make good
(derivation) honoring, observance

adj. observed, examined

v. observe, watch; examen; notice, comment, remark; adhere, keep, respect, obey

v. observe, watch, study; monitor, supervise; discern; keep, honour; fulfill religious commandments; follow, abide by; remark, comment