Gothic verbs have the most complex conjugation of any attested Germanic language. Most categories reconstructed for the Proto-Germanic verb system are preserved in Gothic. Knowledge of the Proto-Germanic verb is itself to a large degree based on Gothic, meaning that its reconstruction may be fragmentary. In conjugations, note that stem-final -b- /β/ and -d- /ð/ change spelling and pronunciation to become -f /ɸ/ and -þ /θ/ respectively at the end of a word. Stem final -g- /ɣ/ also presumably became /x/, but the spelling does not change. Similarly, verb stems ending in -ái-, -áu-, -ē-, -iu-, and -ō- become -aj-, -aw, -ai-, -iw, and -au- respectively, before vowels. Expected *áij, *áuw, and *iuw are always simplified into ái, áu, and iu (respectively). Strong verbs Germanic language strong verbs are verbs that change the vowel in the stem to form the past and past participle, rather than add a suffix. For an English example, contrast fall-fell-fallen (strong) from fell-felled (weak). The following is a table of all the different types and subtypes of strong verbs. The "general" stem is used for the present tense, infinitive and imperative. The "past 1" stem is used for the past tense indicative singular, and the "past 2" is used for the dual and plural indicative past as well as the past optative past in all numbers. Classes 5 and 6 have a small subclass of verbs that use the consonant suffix -j- in the general form, but drop it elsewhere Reduplicating/ Class 7 strong verbs that begin with a vowel simply add aí- as a prefix, without adding a consonant to reduplicate or separate the "aí" prefix from the stem vowel. The following strong verbs are extant in Gothic: Class 1: beidan "to await" (báiþ), beitan "to bite", digan "to knead", dreiban "to drive" (dráif), greipan "to seize", hneiwan "to bow", bileiban "to remain" (biláif), ga-leiþan "to go", urreisan "to arise", skeinan "to shine", disskreitan "to rend", gasmeitan "to smear", sneiþan "to cut", speiwan "to spit", steigan "to ascend", sweiban "to cease" (swáif), weipan "to crown", inweitan "to worship"; Class 1, before h, ƕ, r: leiƕan "to lend", ga-teihan "to tell", þeihan "to thrive", þreihan "to press upon", weihan "to fight"; Class 2a: ana-biudan "to bid" (anabáuþ), biugan "to bend", driugan "to serve as a soldier", driusan "to fall", giutan "to pour", hiufan "to mourn", dishniupan "to break asunder", kiusan "to test", kriustan "to gnash";