Past form vowel change from "a" to "u"

swim swum	sing sang	began begun
run ran	sank sunk	drink

past forms end in "ght". If there is an "a" in the infinitive there is an "a" in the past forms

fight fought	brought brought	think thought
buy	taught taught	catch

Past participle end in "n"

ride rode	write written	bite bit
be	drove driven	wake woken
break broke	choose chose	fall fallen
forget forgot	forgive forgiven
give gave	froze frozen	shake shaken
take took	eat eaten	speak spoke
fly flew	knew known	throw thrown
blow blown	steal stolen	see
wear wore	tear torn	lie lain

No change in form

cost	cut	let
read	hit	put
shut

Past participle vowel changes to "o"

do	go	come come
become became

Changes in past forms and the past and past participle are the same

have	found found	slid slid
told told	sell sold	won won
hang hung	sit sat
stand stood	said	lay laid
lead	fed fed	fled fled
made	paid	held

Past forms end in "t"

lose lost	shoot shot	built built
kept	meet	slept
bent	sweep	sent
spent	lend	bend
leave	get	felt felt