[annie123 (OP)]

As per topic heading .....

[chiralSPO]

typically, the omega will be followed by a number (like 3, or 5)

omega (ω) is the last letter of thee Greek alphabet, and is used in chemistry to denote the end of a long chain. an ω-3 unsaturated fatty acid is one that has a C=C bond three bonds in from the last carbon of the chain.

https://en.wikipedia.org/wiki/Omega-3_fatty_acid

[annie123 (OP)]

Thanks. I knew it was the last letter but didn't know the connection. Interesting!

[Bored chemist]

The practice starts from the idea of referencing the atoms in a chain like that, but starting from the other end (i.e. starting from the end with the acid group).
The carbon next to the acid group is the "alpha carbon" the one that is next bar one is the "beta carbon" and so on.
It's not easy (or particularly important in this case) to say how long the chain is, but what matters is that you are 3 carbons in from the end.

And it means that
ω-3
should be read as "omega minus three" rather than "omega three" and "ω3" is wrong.

[Colin2B]

....omega (ω) is the last letter of thee Greek alphabet,

I am glad that thou didst explaneth that 

[chiralSPO]

....omega (ω) is the last letter of thee Greek alphabet,

I am glad that thou didst explaneth that 

For soothe, my olde eeee key is stucke. thee = the