lpetrich
Contributor
Even more evident is shared patterns of irregularity, especially
Suppletion - using different word forms for different parts of a paradigm.
English has some of that, like some verb conjugations and comparison paradigms, like go - went - gone, good - better - best, bad - worse - worst. For "to be", it's a mixture of suppletion and incomplete reduction of ancestral conjugations by the standards of English verbs.
Suppletive comparison paradigms are found in other Germanic languages, in Latin and Romance, in Celtic, in Slavic, etc.
Though other Germanic languages don't have the suppletion that English has for "to go", the Romance languages have plenty of suppletion there.
Suppletion can be traced back to Proto-Indo-European for some verbs, like the copula verb ("to be").
Indo-European copula
The two main PIE roots are *es- and *bhuH- (> is, be), joined by some others in some of the dialects, like *wes- in Germanic.
Dawn of Verbal Suppletion in Indo-European Languages -- discussing several examples. Suppletive verbs mostly have very general sorts of meanings, as do adjectives with suppletive comparisons in the dialects.
FIrst and second person pronouns are also suppletive in the dialects, with suppletion in them reconstructed for PIE. English I/me, thou/three, we/us. The PIE singular pronouns are *egho-/*me- and *tu-/*te-, with the plural ones being more difficult to reconstruct.

English has some of that, like some verb conjugations and comparison paradigms, like go - went - gone, good - better - best, bad - worse - worst. For "to be", it's a mixture of suppletion and incomplete reduction of ancestral conjugations by the standards of English verbs.
Suppletive comparison paradigms are found in other Germanic languages, in Latin and Romance, in Celtic, in Slavic, etc.
Though other Germanic languages don't have the suppletion that English has for "to go", the Romance languages have plenty of suppletion there.
- Italian: andare -- pres. vado, vai, va, andiamo, andate, vanno -- impf. andavo, pret. andai, fut. andrò
- Spanish: ir -- pres. voy, vas, va, vamos, vais, van - impf. iba, pret. fui, fut. iré
- French: aller -- pres. vais, vas, va, allons, allez, vont - impf. allais, pret. allai, fut. irai
Suppletion can be traced back to Proto-Indo-European for some verbs, like the copula verb ("to be").

The two main PIE roots are *es- and *bhuH- (> is, be), joined by some others in some of the dialects, like *wes- in Germanic.
Dawn of Verbal Suppletion in Indo-European Languages -- discussing several examples. Suppletive verbs mostly have very general sorts of meanings, as do adjectives with suppletive comparisons in the dialects.
FIrst and second person pronouns are also suppletive in the dialects, with suppletion in them reconstructed for PIE. English I/me, thou/three, we/us. The PIE singular pronouns are *egho-/*me- and *tu-/*te-, with the plural ones being more difficult to reconstruct.