The present work was an analysis of two important English grammatical categories: tense and aspect. I tried to formulate the history of the development of these categories and systematize the knowledge about them and their main elements that are used for expressing tenses and aspects – the Past Tense and Past Participle of the regular and irregular verbs.
Also in this work I indicated the tendency to increasing the number of regular, and, accordingly, the reduction of irregular verbs in Modern English. I also tried to divide the most common patterns of irregular verbs’ conjugation into 13 groups according to their past forms and Participles. The term “aspect” and its peculiarities were described in the last chapter.
Appendixes attached show the frequency of the usage of English verbs and of irregular verbs patterns.
The system of the English verbs has been in existence for centuries and it is still developing now. The number of verbs in English increased by 20 times and it is still growing. Now there are more than million words in English lexis, and the number of verbs is enormous, too. That is why the examination of the system of the verbs is important in modern linguistics.
The most common lexical (notional) verbs in Modern English
and the frequency of their usage
according Saakyan 
List of Irregular verbs
Group 1. Verbs that have the same form in Infinitive, Past Tense and Past Participle.
Group 2. The Past Tense and Past Participle forms are composed with the help of the flexion “-ought”.
Group 3. The final consonant “-d” in the stem changes into “-t” in both forms.
Group 4. The root vowel “-i-“ changes into diphthong “-ou-”.
Group 5. The root vowel before “-ng” changes into “-u-“.
Group 6. The long [i:] changes into the short [e].
Group 7. The verbs save their vowel but accept the consonant “-t” at the end of the stem.
Group 8. The Past Simple and Participle II forms do not obey the principles of the Groups 1-7, but they still coincide.
Group 9. One of the forms coincides with the infinitive.
Group 10. The root vowels change according to the pattern:
“-i- > -a- > -u-“.
Group 11. In the Past Simple form the verb changes the root vowel. Participle II has “-n-“ at the end of the stem.
Group 12. The Past Simple form does not coincide with the infinitive and with the Participle II. Participle II has “-en-“ at the end of the stem; its root vowel coincides with the infinitive’s root vowel.
Group 13. The Past Simple and Participle II forms do not obey the principles of any patterns.
The division of irregular verbs.
On the diagrams below we can see the frequency of patterns used for creating the past forms of the irregular verbs. The Groups mentioned are pointed in Appendix 2