Strong verbs form their preterite tense (and past participle) by means of a change of the root vowel, inherited from Proto-Indo-European, which is called vowel-gradation or ablaut. Thus for example, ‘ic fare’ meant ‘I go’, ‘ic fōr’ ‘I went’, ‘wē fōron’ ‘we went’. Since however there are often two different vowels in the preterite (‘ic healp’ ‘I helped’ and ‘wē hulpon’ ‘we helped’), with strong verbs it is necessary to distinguish four (instead of three as it is with the weak verbs) principal forms:
1) the Infinitive, or Present Indicative, Ist person, sg.
2) the Preterite Indicative 1st (or 3rd) Singular,
3) the Preterite Indicative Plural,
4) the Past Participle.
Strong verbs are divided into seven classes, each having a distinct set or pattern of the root vowels in its principal parts, different from any other class. Each of these may be further subdivided into one or two sub-classes as the result of additional sound changes.
Class I:
ī–ā– i –i
drīvan
drāf
drifon
drifen
Class II:
ēo–ēa– u – o
a) crēopan
b) būgan
crēap
bēag
crupon
bugon
cropen
bogen
Class III:
eo – ea – u – o
e – ea(æ) –u–o
i – a(o) –u – u
feohtan
helpan
bregdan
findan
feaht
healp
brægd
fand
fuhton
hulpon
brugdon
fundon
fohten
holpen
brogden
funden
Class IV:
e – æ –ǣ– o
brecan
bræc
brǣcon
brocen
Class V:
e/i – æ – ǣ – e
a) sprecan
b) sittan
spræc
sæt
sprǣcon
sǣton
sprecen
seten
Class VI:
a – ō – ō – a
faran
fōr
fōron
faren
Class VII comprised old reduplicated verbs which in historical times formed their Preterite with the vocalism -ē- or -ēo-, and the Past Participle of which had the vocalism of the Present Tense.
hātan
hēt
hēton
hāten
(call)
cnāwan
cnēow
cnēowon
cnāwen
(know)
grōwan
grēow
grēowon
grōwen
(grow)
fēallan
fēoll
fēollon
fēallen
(fall)
The Present Indicative was formed by means of the following set of ending:
Sg.
Pl.
1.
- e
↘
2.
- (e)st
→ aþ
3.
- (e)þ
↗
In addition to that, in the 2nd and 3rd person sg., the root vowel would undergo the following changes (i-umlaut/mutation);
ĕo/ēo > ĭe/īe
crēopan
crīepst
crīepþ
(creep)
ĕa/ēa > ĭe/īe
feallan
fielst
fielþ
(fall)
ǔ/ū > y/ӯ
cuman
cymst
cymþ
(come)
ă/ā > æ/ǣ
cnāwan
cnǣwst
cnæwþ
(know)
ō > ē
grōwan
grēwst
grēwþ
(grow)
e > i
helpan
hilpst
hilpþ
(help)
Note: But i/ī, ēand ǣ would remain unchanged.
The Present Indicative of the verbs drīfan (drive), crēopan (creep), helpan (help), faran (go) is then as follows:
Singular
1. (ic)
drīfe
crēope
helpe
fare
2. (þu)
drīfst
crīepst
hilpst
fær(e)st
3. (hē)
drīfþ
crīepþ
hilpþ
fær(e)þ
Plural
1 – 3 (wē, gē, hīe)
drīfaþ
crēopaþ
helpaþ
faraþ
The Preterite Indicative is formed by means of the following set of ending:
Sg.
Pl.
1.
-
↘
2.
- e
→ on
3.
-
↗
The paradigm:
Singular
1.
drāf
crēap
healp
fōr
2.
drife
crupe
hulpe
fōre
3.
drāf
crēap
healp
fōr
Plural
1 – 3
drifon
crupon
hulpon
fōron
Note: In Preterite, 1st and 3rd person sg. were always identical; the root vowel of the 2nd person sg. was always that of the plural.