The Northern Subject Rule is a grammatical pattern that occurs in Northern English and Scots dialects. Present-tense verbs may take the verbal ‑s suffix, except when they are directly adjacent to one of the personal pronouns I, you, we, or they as their subject. As a result, they sing contrasts with the birds sings; they sing and dances; it's you that sings; I only sings.
In the modern Northern English dialects, this pattern varies and now competes with standard forms.
Furthermore, other non-standard dialectal patterns are found that developed separately from the Northern Subject Rule. These include, for example:
Some controversy surrounds its origin. Some scholars (e.g., Graham Isaac) argue that it developed out of the Old English verbal endings by way of Northern Middle English, but others (e.g., H. Tristram) argue that it could be a language-contact transfer feature from the Brythonic language historically spoken in that area. Graham Shorrocks notes that a similar use of the historic present occurs in some dialects of north Germany, citing Gordon (1966) and Wakernagel-Jolles (1971).
This is part of the greater debate whether the Celtic languages have had any influence on the structure of English due to the Celtic population learning the English language rapidly but imperfectly after the coming of the Angles. Some linguists have expressed a very strong opinion in favor of the language contact theory. John McWhorter for instance called the Northern Subject Rule a "bizarre trait", and claims that similar phenomena are otherwise only known in VSO languages (like Brythonic), and rare even in that case.
Newfoundland English and at least some Hiberno-English dialects, the dialect of Wexford for example, follow a similar pattern.