The standard spelling, grammar, and punctuation of Scottish English tend to follow the style of the Oxford English Dictionary (OED). However, there are some unique characteristics, mainly in the phonological and phonetic systems, many of which originate in the country's two autochthonous languages, the Scottish Gaelic language and Lowland Scots. The speech of the middle classes in Scotland often conforms to the grammatical norms of the written standard, particularly in situations that are regarded as formal. Highland English is slightly different from the variety spoken in the lowlands in that it is more phonologically, grammatically, and lexically influenced by a Gaelic substratum.