Is & Tha

Gàidhlig has two verbs for "To Be" - Is and Tha. So what's the difference. Well basically the rule is - To say a person or thing is a person or thing use the form IS. To say a person or thing is something else use the form THA.
Examples
Is mise Pòl - I am Paul
Tha mi fuar - I am cold
Personal Pronouns
Mi - I
Thu - You (singular)
E - He
I - She
Sinn - We
Sibh - You (plural)
Iad - They
Variants of Tha
Positive - Tha
Negative - Chan eil
Interrogative - Am bheil
Negative Interrogative - Nach eil
Examples
Chan eil mi sgith - I'm no tired
Am bheil thu sgith - Are you tired?
Nach eil thu sgith? Aren't you tired?
Emphatic Pronouns
Mise - Me
Thusa - You (singular)
Esan - He
Ise - She
Sinne - We
Sibhse - You (plural)
Iadsan - They
Variants of Is
Positive - Is
Negative - Cha
Interrogative - An
Negative Interrogative - Nach
Examples
Cha mhise Domhnall - I'm not Donald
An tusa Pòl - Are you Paul?
Nach esan Iain - Isn't he Ian?
N.B.
Cha becomes chan before a vowel & lenites where possible (except D,S,T).
An becomes Am before B,F,M,P
Examples
Chan esan (chan before a vowel)
Cha mhise (lenites the m)
Cha sinne (no lenition because of S)