Is tu in spanish singular?
Yes. It just means 'your'.
'You' can be (singular) 'tu' or 'usted' (plural) 'vosotros/as' or 'ustedes' The first and third examples are informal; second and fourth, formal. Their corresponding possessives ('your') are: 'tu' (singular) 'tus' (plural) 'su' (singular) 'sus' (plural) 'vuestro/a' (singular, male/female) 'vuestros/as' (plural, male/female) 'su' (singular) 'sus' (plural) NB that the singular and plural, male/female, relate to the relevant noun. If you mean (erroneously) 'you're' = 'you are', I suggest you ask the question again