These are pretty well all the words which you are likely to come across which are pronounced with a long /ɑː/ in RP, but a short /a/ in other variants of English. For example, in many accents, the words 'pass' and 'mass' rhyme, whereas in RP 'mass' has a short vowel /mæs/ but 'pass' has a long vowel, /pɑːs/. after aghast aunt ask bask basket bastard bath blast brass calf cast castle clasp class craft draft draught fast fasten father flask gasp ghastly giraffe glass graft graph* grasp grass half halve last lather laugh mask mast master nasty pass past pasteurise pastime pastor pastoral pasture path plaster raft rafter rascal raspberry rather shaft staff task vast *Also any word which ends in -graph, e.g. photograph, telegraph Note that other words written with 'ar', such as car, far, farm, park and so on, are also pronounced with /ɑː/ in RP. Please feel free to ask if you have any other questions about RP, and I'll do my best to help.