Noun

(en noun)

The act of observing, and the fact of being observed.

*

, title=(The Celebrity), chapter=5 , passage=But Miss Thorn relieved the situation by laughing aloud,

* {{quote-magazine, year=2012, month=March-April, author=(Jeremy Bernstein)

, volume=100, issue=2, page=146, magazine=(American Scientist) , title= A Palette of Particles , passage=The physics of elementary particles in the 20th century was distinguished by the observation of particles whose existence had been predicted by theorists sometimes decades earlier.}}

The act of noting and recording some event; or the record of such noting.

A remark or comment.

* Shakespeare

That's a foolish observation .

* Alexander Pope

To observations which ourselves we make / We grow more partial for the observer's sake.

A judgement based on observing.

Performance of what is prescribed; adherence in practice; observance.

* Jeremy Taylor

We are to procure dispensation or leave to omit the observation of it in such circumstances.

Noun

(en noun)

An action or statement in response to a stimulus or other event

The announcement of the verdict brought a violent reaction .

You were in the courtroom. What is your reaction ?

When I last tried to eat strawberries I had a terrible allergic reaction .

(chemistry) A transformation in which one or more substances is converted into another by combination or decomposition

In this reaction , the acid and base will neutralize each other, producing a salt.