Inflection, a part of derivation in its wider sense, is separated from derivation properly so called, or from derivation in its limited sense. The degrees of comparison, or certain derived forms of adjectives; the ordinals, or certain derived forms of the numerals; the diminutives, &c., or certain derived forms of the substantive, have been separated from derivation properly so called, and considered as parts of inflection. I am not certain, however, that for so doing there is any better reason than mere convenience. Derivation proper, the subject of the present chapter, comprises all the changes that words undergo, which are not referable to some of the preceding heads. As such, it is, in its details, a wider field than even composition. The details, however, are not entered into. § 372. Derivation proper may be divided according to a variety of principles. Amongst others-- I. _According to the evidence._--In the evidence that a word is not simple, but derived, there are at least two degrees. a. That the word _strength_ is a derived word I collect to a certainty from the word _strong_, an independent form, which I can separate from it. Of the nature of the word _strength_ there is the clearest evidence, or evidence of the first degree. b. _Fowl_, _hail_, _nail_, _sail_, _tail_, _soul_; in Anglo-Saxon, _fugel_, _hægel_, _nægel_, _segel_, _tægel_, _sawel_.--These words are by the best grammarians considered as derivatives. Now, with these words I cannot do what was done with the word _strength_, I cannot take from them the part which I look upon as the derivational addition, and after that leave an independent word. _Strength_ -th is a true word; _fowl_ or _fugel_ -l is no true word. If I believe these latter words to be derivations at all, I do it because I find in words like _harelle_, &c., the -l as a derivational addition. Yet, as the fact of a word being sometimes used as a derivational addition does not preclude it from being at other times a part of the root, the evidence that the words in question are not simple, but derived, is not cogent. In other words, it is evidence of the second degree. II. _According to the effect._--The syllable -en in the word _whiten_ changes the noun _white_ into a verb. This is its effect. We may so classify derivational forms as to arrange combinations like -en (whose effect is to give the idea of the verb) in one order; whilst combinations like -th (whose effect is, as in the word _strength_, to give the idea of abstraction) form another order.