Under the Northern subject rule (NSR), the suffix ""-s"" (which in Standard English grammar only appears in the third person singular present) is attached to verbs in many present and past-tense forms (leading to, for example, ""the birds sings""). More generally, third-person singular forms of irregular verbs such as "to be" may be used with plurals and other grammatical persons; for instance "the lambs is out". In modern dialects, the most obvious manifestation is a levelling of the past tense verb forms "was" and "were". Either form may dominate depending on the region and individual speech patterns (so some Northern speakers may say "I was" and "You was" while others prefer "I were" and "You were") and in many dialects especially in the far North, "weren't" is treated as the negation of "was".