Possible to observe: observable phenomena; an observable change in demeanor. See synonyms at noticeable
Deserving or worthy of note; noteworthy: an observable anniversary.
noun
A physical property, such as weight or temperature, that can be observed or measured directly, as distinguished from a quantity, such as work or entropy, that must be derived from observed quantities.
derivatives
ob·serv́a·bly
adverb
The American Heritage® Dictionary of the English Language, Fourth Edition