It is affected by person, number, gender, tense, mood and voice.
Bulgarian verbs are conventionally divided into three conjugations according to the thematic vowel they use in the present tense: In a dictionary, Bulgarian verbs are listed with their first-person-singular-present-tense form, due to the lack of an infinitive.
The stem of the verb is what is left of the citation form after removing its final letter.
This change is not limited solely to the present tense and happens always before /i/, /ɛ/ and the yat vowel.
Strictly speaking, verbs from the third conjugation are athematic, because the personal endings are added directly to the stem with no thematic vowel in between.
* The consonants к (/k/) and г (/g/) change to ч (/tʃ/) and ж (/ʒ/) before the front vowels е (/ɛ/) and и (/i/).
Additionally, after ж (/ʒ/), ч (/tʃ/) and ш (/ʃ/) the stressed yat vowel can be pronounced either as /a/ (as above) or as /ɛ/.
Verbs from the third conjugation use no thematic vowel, the endings are added directly to the stem.
In the first and second conjugation, verbs are additionally divided into classes according to the thematic vowel they use.
In the third conjugation, verbs are divided into classes according to the final vowel of the stem.
The stems of these verbs end in д (/d̪/), т (/t̪/), с (/s/), з (/z/) and к (/k/).
Although the stem of the verb тъка ends in к (/k/), it is not part of this class, it belongs to the next one.
An important feature of regular verbs from the first class is that the stress always moves on the last syllable of the stem (unless it is already there).
* The consonant к (/k/) changes to ч (/tʃ/) before the front vowel е (/ɛ/).
The verbs (съ-)блекá, влекá, (в-)ля́за and секá have the old yat vowel in the stem, which alternates between я (/ja/) and е (/ɛ/) according to the pronunciation in the eastern dialects.
These verbs use the thematic vowel а (/a/ or /ə/) between the stem and the personal endings.
This class is almost identical to the previous one, the only difference is that the citation form ends in я.
The stems of these verbs end in one of the consonants ж /ʒ/, ч /tʃ/ or ш /ʃ/, which in the aorist change to з/г (/z,g/), k (/k/) and с (/s/) respectively.
The verb режа has the yat vowel, which alternates between я (/ja/) and е (/ɛ/).
The verbs глождя (глозгах), дращя (драсках) and пощя (посках) used to belong to this class but now have completely migrated to the second conjugation.
Stems ending in -ем (/ɛm/) are also considered to belong in this class since they do not use a thematic vowel.
They are a special case because the stem loses the м (/m/) before adding the personal endings.
These verbs are characterized by the fact that the stress always falls on the thematic vowel across all forms, not exclusively in the aorist.
The class contains 27 main verbs: All verbs conjugate in the same fashion (without a thematic vowel, simply by adding the personal endings directly to the stem), nevertheless, Bulgarian grammar books divide them into two classes, depending on the final vowel of the stem.
All regular verbs, regardless of conjugation, form the imperative mood in the same way: Some verbs, most notably stems ending in з (/z/) from the first class of the first conjugation, and a few other frequently used ones, use only the bare stem without a thematic vowel: * The yat vowel changes to е (/ɛ/).
Only verbs from the first class of the first conjugation form it somewhat differently: the thematic vowel о (/o̝/) is removed and the л (/ɫ/) is added directly to the stem with some additional changes, namely: The past active aorist participle keeps the stress of the past aorist, either shifted or not.
Although the past passive participle is formed from the past aorist, it does not have a stress shift, it always keeps the stress of the present tense, except for first conjugation verbs from the first class, and the verbs греба and гриза which used to belong to the first class.
2 The consonant к (/k/) changes to ч (/tʃ/) before the front vowel е (/ɛ/).
Verbs from the first and second conjugation use the thematic vowel е (/ɛ/) between the stem and the ending -йки (/jkʲi/).
Stems ending in н (/n/) from the second class of the first conjugation, and stems ending in е (/ɛ/), и (/i/), у (/u/) and ю (/ju/) from the seventh class use only the past imperfect to form the verbal noun.