In English, the form which the Latin word _numerus_ takes is _number_; in Spanish, _nombre_. The b makes no part of the original word, but has been inserted for the sake of _euphony_; or, to speak more properly, by a euphonic process. The word euphony is derived from εὖ (_well_), and φώνη (_fônæ_, a voice). § 134. In the words _give_ and _gave_ we have a change of tense expressed by a change of vowel. In the words _price_ and _prize_ a change of meaning is expressed by a change of consonant. In _clothe_ and _clad_ there is a change both of a vowel and of a consonant. In the words _to use_ and _a use_ there is a similar change, although it is not expressed by the spelling. To the ear the verb _to use_ ends in z, although not to the eye. All these are instances of the _permutation_ of letters. _Permutation of Vowels._ a to ĕ, as _man_, _men_. a to oo, as _stand_, _stood_. a to u, as _dare_, _durst_. a to ē, as _was_, _were_. ea to o, as _speak_, _spoken_. ea = ĕ to ea = ē, as _breath_, _breathe_. ee to ĕ, as _deep_, _depth_. ea to o, as _bear_, _bore_. i to a, as _spin_, _span_. i to u, as _spin_, _spun_. ī = ei to o, as _smite_, _smote_. i = ei to ĭ, as _smite_, _smitten_. i to a, as _give_, _gave_. i = ei to a, as _rise_, _raise_. ĭ to e, as _sit_, _set_. ow to ew, as _blow_, _blew_. o to e, as _strong_, _strength_. oo to ee, as _tooth_, _teeth_. o to i, as _top_, _tip_. o to e, as _old_, _elder_; _tell_, _told_. ŏ to e, as _brother_, _brethren_. ō = oo to i, as _do_, _did_. o = oo to o = ŭ, as _do_, _done_. oo to o, as _choose_, _chose_. _Permutation of Consonants._ f to v, _life_, _live_; _calf_, _calves_. þ to ð, _breath_, _to breathe_. þ to d, _seethe_, _sod_; _clothe_, _clad_. d to t, _build_, _built_. s to z, _use_, _to use_. s to r, _was_, _were_; _lose_, _forlorn_. In _have_ and _had_ we have the _ejection_ of a sound; in _work_ and _wrought_, the _transposition_ of one. _Permutation of Combinations._