Modal verbs or modals are concerned with our relationship with someone else. Modal have 2 major functions which can be defined as primary and secondary.
Primary function of Modal Verbs. In their primary function MVs closely reflect the meanings:
A) of ability (can/could). / can lift 25 kg/I can type.
B) of permission (may/might). You may leave early.
C) of prediction (will/would) - (shall/should). It will rain soon.
D) Of escapable obligation or duty (should/ought to). You should (ought to) do as you are told.
E) Of inescapable obligation. You must be quiet. F) Of absence of obligation. You needn't wait.
Secondary function of MVs
In their secondary function nine of modal auxiliaries can be used to express the degree of certainly/uncertainly a speaker fuels about a possibility. They can be arranged on a scale from the greatest uncertainty (might) to the greatest certainty (must).
can be right
should have been right
You ought to
The category of aspect
The aspective meaning of the verb reflects the mode of the realization of the process. The opposition of the continuous forms of the verb to the non-continuous represents the aspective category of development. The marked member of the opposition is the continuous. It is built by the auxiliary be plus the Present Participle. In symbolic notation it is represented by the formula be...ing. The categorial meaning of the Continuous is "action in progress".
The unmarked member is the indefinite, which leaves the meaning unspecified. Four combinations of the continuous and the indefinite are possible in principle in Modern English. E.g.: While I was typing, Mary and Tom were chatting in the adjoining room. While I typing, Tom and Mary were chatting in the adjoining room. While I was typing, they chatted in ... While I typed, they chatted.
Clearly, the difference in meaning cannot lie in their time denotations. The time is shown by their time signals (were - ed). The meaningful difference consists in the following: the continuous shows the action in the very process of its realization; the indefinite points it out as a mere fact. We speak of the morphological category of the verb, but care should be taken that the character of the development of the action may also be expressed lexically or remain implicit. E.g.: When I entered the room he was writing a letter. He wrote and wrote the letter (lexically). When I entered the room, he wrote a letter.
In the last sentence the form of the verb doesn't express the Continuous aspect explicitly because the speaker isn't interested in the action, but in the object of the action. Traditionally forms like "is writing" are called Present, Past, Future Continuous Tense, but that is not quite right. Such forms should be called Present Tense, Continuous aspect (is writing). The Present Tense is modified by the Continuous. It the Continuous were a special tense then we should speak of 2 tenses at once. But the action can't develop in 2 tenses at once. If the actions are not progressive by themselves (if they are not shown as progressive), the description will go without the continuous forms. The Continuous refers a to a definite time-point. The category of development undergoes explicit various reductions:
1. The unlimitive verbs are very easily neutralized Ex. The night is wonderfully silent. The stars shine with a fierce brilliancy, the Southern Cross and wind. The Duke's face seemed blushed, and more lined than some of his recent photographs showed. He held a glass in his hand.
2. As to the statal verbs, their neutralization amounts to a grammatical rule. They are so called "never-used-in-the-Continuous" verbs: a) the unique "to be" and "to have"; b) verbs of possession, verbs of relation, of physical perception, of mental perception
3. Worthy of note is the regular neutralization with the introductory verb supporting the participial construction of parallel action. Ex. He stood smoking a pipe. Not normally: He was standing smoking.
4. On the other hand, the Continuous can be used to denote habitual, recurrent actions. Continuous verb forms are more expressive than non-continuous - they are used in emotional speech. Ex.: He is always complaining.
5. Special note should be of the broadening use of the Continuous with unlimitive verbs. Here are some typical examples. Ex. I heard a rumor that a certain member here present has been seeing the prisoner this afternoon (E.M. Forster). I had a horrid feeling she was seeing right through me and knowing all about me. What matters is, you're being damn fools (A.Hailey)
6. Compare similar transpositions in the expressions of anticipated future. E.g.: Dr. Aarons will be seeing the patient this morning (A.Hailey). Soon we shall be hearing the news about the docking of the spaceships having gone through.
Since the neutralization of the Continuous with these verbs is quite regular, we have an emphatic reduction serving the purpose of speech expressiveness.
The Category of voice
The category of Voice expresses relations between the subject and the object of the action or between the subject and the action.
The opposition of the passive form of the verb to the active form of the verb expresses the voice of the English Verb. E.g.: writes - is written. The passive form is the strong member of the opposition. On the plane of expression it is marked by the combination of the auxiliary be with the Past Participle of the notional verb. The active form as a weak member of the opposition expresses "non-passivity". The Active Voice shows that the subject of the sentence is the doer of the action. The Passive Voice shows that the subject is acted upon. The agent may be expressed in the sentence and it's usually introduced with the help of the preposition by. Ex. The book is written by a young writer.
The sentence with the passive voice may include a means of the action, which is introduced, with the help of the conjunction with. Ex. The book is covered with a newspaper.
The category of voice has a much broader representation in thesystem of the English verb than in the system of the Russian verb, since in English not only transitive but also intransitive verbs can be used.
In accord with their relation to the passive voice, all the verbs can be divided into 2 large sets: the set of passivized verbs and the set of non-passivized verbs. In particular the passive is alien to many verbs of the statal subclass, such as have, belong, cost, resemble, fail, misgive, etc.
The demarcation line between the passivized and non-passivized set is not rigid, and the verbs of the non-passivized set may migrate into the passivized set in various contexts. Ex. The bed has not been slept in. The house seems not to