Trøndersk (also trønder(-dialekt), especially locally, or trøndsk, especially in linguistic literature) is the Norwegian dialect spoken in the region Trøndelag, the district Nordmøre and the municipality Bindal in Norway as well as in Frostviken in northern Jämtland, Sweden, which was colonized in the 18th century by settlers from Nord-Trøndelag and transferred to Sweden as late as 1751. The dialect is among other things perhaps mostly characterized by the use of apocope, palatalization and the use of retroflex flaps (thick L). Historically it also applied to contiguous regions of Jämtland and Härjedalen (which sometimes but rarely are referred to as "Øst-Trøndelag" by locals and Norwegians) in Sweden as well.
The word trøndersk is an adjective describing a Trønder (a person from Trøndelag) or anything coming from or relating to Trøndelag (including the dialect).
There is no standard ortography for trøndersk. The dialect includes several more or less distinct sub-dialects. Some might consider it more accurate to describe trøndersk as a language than as a dialect (cf. Jamtlandic), but this is not common among linguists, for both linguistic and political reasons.
Some of the more conspicuous variations of these dialects of Norwegian, in addition to the aforementioned apocope and palatalization, are that most of the personal pronouns are pronounced differently than in Standard Norwegian, e.g. Trondheim dialect: 1st person singular nominative /æ:/ (Standard Norwegian "eg" (Nynorsk) / "jeg" (Bokmål)) or 2nd person plural accusative /dåkk/ or /dåkker/, commonly spelled "dokker" or "dåkker" (Standard Norwegian "dykk" (Nynorsk) / "dere" (Bokmål)). Variation among personal pronouns are common in most Norwegian dialects.
The sub-dialects of trøndersk which are the furthest from Standard Norwegian are found in the region Innherred.; notably in Verdal and Skogn. Here the everyday language bears some resemblance to both Swedish, Icelandic and Old Norse. However, the urbanisation, globalisation, immigration and americanisation is a serious threat to trøndersk with sub-dialects, as well as to other languages/dialects/sub-dialects (and generally to local and regional culture all over the world). Many people (among them locals) are concerned that this leads to less diversity and makes it steadily harder to decide where people come from based on their discourse. A side effect of this degradation of dialects is that one might guess the speaker's age from his or her dialect.