A motto is described as a brief statement used to express a principle, goal, or ideal. It is a sentence, phrase, or word of appropriate character inscribed on or attached to an object, and is, quite often, a maxim adopted as a guide to one's conduct.
In terms of Scottish heritage, a motto is a unifying phrase for all members of a particular family or clan.
Scottish heraldry is one of the most tightly controlled in the world, as it is one of the few countries where heraldry is protected by law which is still actively enforced, and this includes the registration of family mottos.
If one is Scottish or of Scots descent, unless one can prove that that one are heir to a properly matriculated Scots coat of arms, then one must matriculate a set at the Lyon Court in Edinburgh. Coats of Arms belong to individuals - there are no family arms in Scotland! The clan arms usually reside with the chief of that clan. This applies to the chief's relatives, including his own immediate family and even his eldest son. All members of the extended family called the "Clan", whether bearing the Clan surname or that of one of its septs; that is all those who profess allegiance to that Chief and wish to demonstrate their association with the Clan. It is correct for these people to wear their chief's armourial crest encircled with a strap and buckle (circlet) bearing their chief s motto or Slogan. The strap and buckle is the sign of the clansman, and one demonstrates membership in the clan by wearing one's chief's crest within the circlet.
As is indicated above, the Motto of Scotland is "Nemo Me Impune Lacessit" (No one harms me with impunity). This defiant Latin phrase is boldly emblazoned above the gates of Edinburgh Castle. The motto is also used by the Chivalric Order of the Thistle, and has also been adopted as the motto of the Royal Scots Dragoon Guards, Royal Scots Greys, Scots Guards, Royal Scots, Cameronians, Black Watch, 42nd Highlanders and the Royal Highland Fusiliers. (The RHF uses the plural form Nemo Nos Impune Lacessit, or "no one harms us with impunity). This motto has also been adopted by St. Andrew's Society's around the world -- a testament to Scottish heritage and culture.
The Motto of Nova Scotia, on the other hand, is "Munit Haec Et Altera Vincit" (One defends and the other conquers). The motto is a reference to the mythical Unicorn (representing Scotland) and the Mi'kmaq individual that support the Coat of Arms of Nova Scotia.
Traditionally, Scottish mottos are in Latin, Gaelic, English and French, though not limited to these four languages.