Old Bulgarian:
It is formed by adding the suffix –jьs and –jes to the root, which can be extended by adding – ѣ
The first way is more ancient and rare while the second is newer, more productive and tends to replace the old one. Thus, the forms made by the first way are called short, and those made by the newer way- long.
The short forms for masculine gender were formed by the suffix –jьs. If the adjective had other suffix, it was dropped and the comparative suffix was added directly to the root. The final –s dropped according to the “Law for opening of the syllable’’ and the final consonant of the root, before the j, was being palatalized.
драгъ>дражь> дражьи
высокъ>вышь > вышьи
сладъкъ>слаждьи
широкъ>ширьи
крѣпъкъ>крѣпльи
The short form of feminines was created with the suffix –jьs. Though, was extended with the vowel и. The ancient consonant s in the suffix after ь mutates to х, which later, due to its position before и changes to ш. Thus the suffix used for forming the comparative form turns to –ьши.
драга>дражьши
высока>вышьши
сладъка>слаждьши
люта>люштьши
The short form of the adjectives in neuter is formed by –jes. After the drop of the final consonant are produced: дражє, вышє, крѣплє, люштє.
The short form of the adjectives in neuter is formed by –jes. After the drop of the final consonant are produced: дражє, вышє, крѣплє, люштє.
The long form is formed by the suffixes mentioned above, but extended with ѣ. If the adjective has other suffix, it is remained and the ѣ is added directly to it. Final positive velars in –ъкъ, -ькъ, -икъ change to ч and the yat vowel itself mutates to а.
мѧкъкъ>мѧкъчаи, мѧкъчаиши, мѧкъчаѥ
горькъ>горчаи, горчаиши, горчаѥ
Long comparative forms have only the adjectives in feminine and neuter. Adjectives in masculine have only short forms.
Czech:
The regular rule to derive a comparative form from an adjectival root is to add the suffix -ejší/-ější . There are palatalizations: p-pj, b-bj, f-fj, v-vj, m-mň, t-t´, d-d´, n-ň, r-ř, k-c, h/g-z, ch-š, sk-št´, ck-čt´..
Some adjectives use the formant -ší with the other type of palatalization:t/t´-c, d/d´-z, s-š, z-ž, n-ň, r-ř, sl-šl, st/st´-št´, zd/zd´-žd´, k,c-č, h/g-ž, ch-š.
Some irregularities: daleký-další, dlouhý-delší, dobrý-lepší, špatný-horší, vel(i)ký-větší, malý-menší.
Polish:
Polish has analytic way of forming the comparative form, by the word bardziei.
The simplest type of comparative morpheme is -sz when the adjective ends in vowel or a consonant or certain clusters. When it ends in cluster, the suffix is -ejsz. Here also occur consonant alternations, similar to those in Czech.
In both western Slavonic languages, there is one particular case: when the root ends in -k or -ok, it is usually dropped or, if it is not, mutated.
Russian:
1) Stems ending in consonants other than -k,-g,-x require the suffix -ейш-.
2) Stems ending in -f,-g,-x require the suffix -айш-; at the same time mutation occurs: г>ж, к>ч, х>ш.
The irregular forms here, again, are inherited alternative roots from the Old Bulgarian: плохой-хуже, хороший-лучше, маленький-меньше.
Slovene:
In Slovene, the usual way- using suffixes, is unproductive (lep-lepši, debel-debelejši). The analytic formation is far more used: bolj + adj (for superiority), manj+adj (for minority).
The unproductive type, mostly monosyllabic stems in positive, are formed as follow: dóber-bôljši, dáleč-dâljši, globòk-glôblji, krátek-krâjši, láhek-lâžji, mâjhen-mânjši, mlâd-mlâjši, nízek-nîžji, ràd-râjši, slàb-slâbši, sládek-slâjši, vélik-vêčji .
Serbian:
Here the comparative grade is formed by adding the suffix -iji-. Some of the palatalizations occurring here are d>-đi , g>-z or -ži , h>-š or -ši , k>-či , t>-ci; -p,-b,-v require an empathetic -l- (-plji-, -blji-, -vlji-).
Some irregular forms are: lep-lepši, dobar-bolji, loš-gori, velik-veći, mali-manji.