observance vs. observation

observance (noun):

the practice of following a custom, rule, law, etc.

an act that is part of a ceremony or ritual

a customary practice, rite, or ceremony observances
a rule governing members of a religious order

an act or instance of following a custom, rule or law: observance of the speed limits
an act or instance of watching

Examples:

observance  of this family tradition would make your grandmother very happy
observance of the smoking ban in public buildings
  

observation (noun):

a statement about something you have noticed : a comment or remark

the act of careful watching and listening : the activity of paying close attention to someone or something in order to get information

something you notice by watching and listening

an act or instance of observing a custom, rule, or law

an act of recognizing and noting a fact or occurrence often involving measurement with instruments 
a record or description so obtained

a judgment on or inference from what one has observed;broadly :  remark, statement

the condition of one that is observed 
— ob·ser·va·tion·al  adjective

— ob·ser·va·tion·al·ly adverb

Examples:

I'm not criticizing that kind of clothing. I'm just making an observation about the style.

Her constant observations about the weather bored me.

These facts based on close observation of the birds in the wild.

Observations made using the telescope have led to new theories.

Some interesting observations came from the study.

He recorded his observations in a notebook.

acknowledge vs. recognize

acknowledge (transitive verb):
to say that you accept or do not deny the truth of existence of (something)
to regard or describe (someone or something) as having or deserving a particular status
to tell or show someone that something (such as a letter or message) has been received
to recognize the rights, authority, or status of
to disclose knowledge of or agreement with
to express gratitude or obligation for <acknowledge a gift
to take notice of  acknowledge my greeting
to make known the receipt of <acknowledge a letter
to recognize as genuine or valid 
Examples:
They acknowledged that the decision was a mistake.
Do you acknowledge that you caused this mess?
They readily acknowledged their mistake.
She won't acknowledge responsibility for her actions
He quickly acknowledges all of my e-mails when he receives them.
Please acknowledge receipt of this letter.
She acknowledged the gift with a card.
She acknowledged his greeting with a smile.

recognize (transitive verb):
to know and remember (someone or something) because of previous knowledge or experience
to accept or be aware that (something) is true or exists
to accept and approve of (something) as having legal or official authority
to acknowledge formally as
to admit as being lord or sovereign
to admit as being of a particular status
to admit as being one entitled to be heard :  give the floor to
to acknowledge the de facto existence or the independence of
to acknowledge or take notice of in some definite way: as
to acknowledge with a show of appreciation 
to acknowledge acquaintance with 
to perceive to be something or someone previously known 
to perceive clearly :  realize

adj: recognizable

adv: recognizably 

noun; recognizability

noun: recognizer 

"The end may justify the means as long as there is something that justifies the end." - Leon Trotsky