be O.E. beon, beom, bion "be, exist, come to be, become, happen," from P.Gmc. *biju- "I am, I will be." This "b-root" is from PIE base *bheue- "to be, exist, grow, come into being," and in addition to the words in English it yielded German present first and second person singular (bin, bist, from O.H.G. bim "I am," bist "thou art"), Latin perfective tenses of esse (fui "I was," etc.), O.C.S. byti "be," Gk. phu- "become," O.Ir. bi'u "I am," Lith. bu'ti "to be," Rus. byt' "to be," etc. It also is behind Skt. bhavah "becoming," bhavati "becomes, happens," bhumih "earth, world."
The modern verb to be in its entirety represents the merger of two once-distinct verbs, the "b-root" represented by be and the am/was verb, which was itself a conglomerate. Roger Lass ("Old English") describes the verb as "a collection of semantically related paradigm fragments," while Weekley calls it "an accidental conglomeration from the different Old English dial[ect]s." It is the most irregular verb in Mod.E. and the most common. Collective in all Germanic languages, it has eight different forms in Modern English:
BE (infinitive, subjunctive, imperative)
AM (present 1st person singular)
ARE (present 2nd person singular and all plural)
IS (present 3rd person singular)
WAS (past 1st and 3rd persons singular)
WERE (past 2nd person singular, all plural; subjunctive)
BEING (progressive & present participle; gerund)
BEEN (perfect participle).
The paradigm in O.E. was:
1st pret. subj.
2nd pret. subj.
3rd pret. subj.
The "b-root" had no past tense in O.E., but often served as future tense of am/was. In 13c. it took the place of the infinitive, participle and imperative forms of am/was. Later its plural forms (we beth, ye ben, they be) became standard in M.E. and it made inroads into the singular (I be, thou beest, he beth), but forms of are claimed this turf in the 1500s and replaced be in the plural. For the origin and evolution of the am/was branches of this tangle, see am and was.