Editing Indo-European ablaut (section)

==Subsequent development==
Although PIE had only this one, basically regular, ablaut sequence, the development in the daughter languages is frequently far more complicated, and few reflect the original system as neatly as Greek. Various factors, such as [[vowel harmony]], assimilation with nasals, or the effect of the presence of laryngeals in the Indo-European (IE) roots as well as their subsequent loss in most daughter languages, mean that a language may have several different vowels representing a single vowel in the parent language.

In particular, the zero grade was often subject to modification from changes in the pronunciation of syllabic sonorants. For example, in Germanic, syllabic sonorants acquired an [[epenthesis|epenthetic]] ''-u-'', thus converting the original zero grade to a new "u-grade" in many words. Thus, while ablaut survives in some form in all Indo-European languages, it became progressively less systematic over time.

Ablaut explains vowel differences between related words of the same language. For example:
* English ''strike'' and ''stroke'' both come from the same IE root ''*streyg-''. The former comes from the e-grade, the latter from the o-grade.
* German ''Berg'' (mountain, hill) and ''Burg'' (castle) both come from the root ''*bʰergʰ-'', which presumably meant "high". The former comes from the e-grade, the latter from the zero-grade. (Zero-grade followed by ''r'' becomes ''ur'' in Germanic.)
Ablaut also explains vowel differences between cognates in different languages.
*English ''tooth'' comes from Germanic ''*tanþ-s'' (e.g. Old English ''tōþ'', Old High German ''zand''), genitive ''*tund-iz'' (Gothic ''tunþus'', but also {{Transliteration|got|aiƕa-tundi}} "thornbush", literally "horse-tooth"). This form is related to Latin ''dens, dentis'' and Greek ''{{lang|grc|ὀδούς}}, {{lang|grc|ὀδόντος}}'', with the same meaning, and is reflected in the English words ''dentist'' and ''orthodontic''. One reconstructed IE form is ''*dónts'', genitive ''*dn̥tés''. The consonant differences can be explained by regular sound shifts in primitive Germanic but not the vowel differences: by the regular laws of sound changes, Germanic ''a'' can originate from PIE ''o'', but ''un'' usually goes back to a syllabic ''n̥''.

:The explanation is that the Germanic and Greek nominative forms developed from the o-grade, the Latin word and the Germanic genitive from the zero-grade (in which syllabic ''n̥'' developed into ''en'' much in the same way as it became ''un'' in Germanic). Going a step further back, some scholars reconstruct ''*h<sub>1</sub>dónts'', from the zero grade of the root ''*h<sub>1</sub>ed-'' 'to eat' and the participle ''-ont-'' and explain it as 'the eating one'.
*English ''foot'' comes from the lengthened o-grade of ''*ped-''. Greek ''{{lang|grc|πούς}}, {{lang|grc|ποδός}}'' and Latin ''pes, pedis'' (compare English ''octopus'' and ''pedestrian''), come from the (short) o-grade and the e-grade respectively.

For the English-speaking non-specialist, a good reference work for quick information on IE roots, including the difference of ''ablaut'' grade behind related lexemes, is [[Calvert Watkins|Watkins]] (2000).<ref>{{cite book |editor-first=Calvert |editor-last=Watkins |editor-link=Calvert Watkins |year=2000 |orig-year=1985 |title=The American Heritage Dictionary of Indo-European Roots |edition=2nd |place=Boston, MA / New York, NY |publisher=Houghton Mifflin Harcourt |isbn=978-039598610-3 }}</ref> (Note that in discussions of lexis, Indo-European roots are normally cited in the e-grade, without any inflections.)