All dictionaries but the Century make envelop the verb, envelope the noun. The Century spells the noun envelop as well as the verb.
According to the Century, Worcester, and the English dictionaries, practise (with s) is the verb, practice (with c) is the noun. The Standard spells both practise, and Webster both practice.
Doubling l.
Worcester and the English dictionaries double a final l in all cases when a syllable is added, Webster, the Century, and the Standard only when the rule requires it. Thus: wool——woollen, Jewel——jewelled, travel——traveller.
Re for er.
The following are the words which Worcester and the English dictionaries spell re, while Webster, the Century, and the Standard prefer er: Calibre, centre, litre, lustre, manœuvre (I. maneuver), meagre, metre, mitre, nitre, ochre, ombre, piastre, sabre, sceptre, sepulchre, sombre, spectre, theatre, zaffre,{.}
English words with our.
The following are the words in which the English retain the u in endings spelled or by American dictionaries. All other words, such as author, emperor, etc., though formerly spelled with u, no longer retain it even in England:
Arbour, ardour, armour, behaviour, candour, clamour, colour, contour, demeanour, dolour, enamour, endeavour, favour, fervour, flavour, glamour, harbour, honour, humour, labour, neighbour, odour, parlour, rancour, rigour, rumour, saviour, splendour, succour, tabour, tambour, tremour, valour, vapour, vigour,.
_____________________________________________________________________