Verbs may be transitive, denoting action, or intransitive, describing a state of being. The verb to be is a typical intransitive verb because it reflects back on its subject. It is also one of the important auxiliary verbs. It combines with almost all verbs, both transitive and intransitive, in their present and past participle forms. It is in dealing with the verb to be that most difficulties arise. A study of this verb and the verb to have, which also acts as an auxiliary, is recommended to all who are interested in good grammar.

The verb always agrees in number with the subject:

A singular verb is necessary when the subject is singular and the complement plural:

The word what takes a singular verb even if its complement is plural:

Words joined to the subject by with, together with, including, as well as, and similar connectives do not affect the number of the verb:

If the word number is used collectively, the verb is singular:

If individual units are referred to, the word number takes the plural verb:

See 'Collective nouns' for further examples.

Tense

There are many tenses with numerous applications, and only a few general recommendations are made here:

1. Describe rocks in the present tense:
   
   
   The sill occupies an unconformity, and its roof rocks are highly altered.
   
   
   
2. Describe events of geological history in the past tense:
   
   
   The magma intruded the unconformity, forming a sill, and shortly after, a hydrothermal system developed in its roof rocks.
   
   
   
3. Describe experimental activities and phenomena in the past tense; they presumably are completed by the time of writing:
   
   
   We heated the charge to 1500°C at 20 kbar, and the mineral assemblage partly melted.
   
   
   
4. Discuss experimental results in both past and present tenses, as appropriate to the conditions and observations:
   
   
   The experiments showed that the mineral assemblage is stable under these conditions.
   
   
   
5. Describe specific conclusions in the past tense to emphasize that they represent special conditions, in contrast to general conclusions, principles, or truths, which should be described in the present tense:
   
   
   The Hawaiian hotspot evidently stayed fixed, even though oceans are spreading and continents are drifting.
   
   
   
6. Refer to other authors in the past tense; they may since have changed their minds - or even died:
   
   
   Darwin (1859) argued for evolution of the species by survival of the fittest.
   
   But, when reference is made to their work by its title, then because the document still exists, discuss its contents in the present tense:
   
   The Origin of Species contains other examples.
   
   
   

Verbals

In English, there are three verb forms, which, in addition to their verb-like functions, perform the work of another part of speech at the same time. These verb forms are the participle, the gerund, and the infinitive.

Participles

An English verb has two participles: the present participle always ending in -ing, as in finishing, and the past participle, which ends in -d, -ed, -n, -en, or -t, as in finished. A participle is a verb form that can act as an adjective:

Dangling participles

Avoid the common error of opening a sentence with a participle, thus misrelating phrases, so that the participle becomes unattached from its correct noun or implies a wrong noun, as in the following examples:

Such sentences with dangling participles range from amusing to ridiculous – where they should be easy to spot. Students may be fragile, but rocks and cratons are remarkably stable.

Make sure that phrases are related to a proper subject in the main clause. This can be done by examining the participles (present participles end in -ing; past participles end in -d or -ed) and asking: Who or what is -ing or -ed? If the answer is not logical, then rewrite the entire sentence.

Care should be taken to avoid the hanging participle, gerundial, or infinitive phrase, that is, one for which the subject is missing. Amusing illustrations have been quoted, such as: Having eaten our lunch, the boat sailed for Quebec; or, When three years old (or, At the age of three), my grandmother died. However, these are no more absurd than the following: Approaching the contact, the phenocrysts decrease in size; On crossing the ridge, the quartz veins appeared at closer intervals; or Reviewing the preceding paragraphs, the Cache Creek Group...

Gerunds

A gerund is a verbal noun: mining, geochemical prospecting.

When used as a subject or object, the gerund should be used with a noun or pronoun in the possessive:

This rule is most often ignored when words are inserted between the preposition and the gerund:

Writers should not allow themselves to fall into this trap. It can be avoided by rewriting the sentence:

Infinitives

This verbal form may be used as a noun, an adjective, or an adverb. It is usually preceded by the word to, which in this case is not a preposition, but the sign of the infinitive.

Split infinitives

The intrusion of an adverb or an adverb phrase between the to and the verb of the infinitive is called the split infinitive. Split infinitives are unpleasant to the ear and jolt the reader by interrupting the action implied by the verb, for example:

The following two examples do not sound so distinctly jarring, but are nevertheless split infinitives:

At times, however, it is permissible for emphasis to split an infinitive when it would be awkward to put the adverb before or after the infinitive.

Auxiliary verbs 'shall' and 'will'

To express the simple future, use the auxiliary shall in the first person and will in the second and third persons. These auxiliaries are reversed to express determination or command, as I will, you shall, they shall. This has always been the rule, but the modern trend is to neglect the shall and the conditional form should and to use instead will and would in the first person, as in I would like to do it rather than I should like to do it. Colloquialism is so strong an influence in the use of these auxiliaries that it is doubtful that fixed rules would help the writer. When in doubt, use will.

Subjunctive

The present subjunctive has the same form as the 'bare' infinitive or imperative: be, save, demand. The subjunctive is rapidly falling into disuse. Its few remaining regular uses include the following:

1. certain common expressions:
   
   come what may if need be
   
   
   
2. legal or quasi-legal language:
   
   I move that the meeting be held in Quebec.
   
   
   
3. conditional sentences where the hypothesis is not a fact:
   
   If I were you, I would write to the Director General today. If he were here, I would tell him what I think of it.
   
   
   
4. the expressions as if and as though, if the hypothesis is not accepted as true:
   
   He spoke of his proposal as if it were a complete solution to the difficulty. He talks as though he knew the location of the 'Lost Lemon Mine'.
   
   
   
5. expressions of uncertainty, doubt, or supposition:
   
   He wondered if he were right.

Active and passive voice

Use the active voice wherever possible. It makes for better and clearer writing. Make the initiator of the action, not the object acted upon, the subject of the sentence:

Douglas mapped the fold belt is the active voice. The fold belt was mapped by Douglas is the passive voice. The passive voice (sometimes referred to as passive construction) is made up of a tense of the verb to be plus the past participle of another verb: I was shown; It is determined that.

In writing, do not change from the active voice to the passive voice, or vice versa, within a sentence or within a paragraph. Indeed, in current scientific writing, the active voice is preferred over the passive voice, and is more concise, avoiding the use of was and by. The sentence: The writer spent the last two field seasons in the area, and it is expected that he will return next year should be written: The writer spent the last two field seasons in the area, and expects to return next year. The corrected sentence is shorter, and avoids a circumlocution.

It is sometimes easy to lose sight of the logical subject of a sentence. Do not begin a sentence with a clause containing an active verb and then introduce a new subject that leads to the use of a passive verb:

Avoid using it as a subject, such as It should be noted that....

The passive voice can be used for certain routine statements: Samples were collected from several localities is just as acceptable as We collected samples from several localities. If the state of the bedrock is the point of significant interest in a report, then it is more acceptable to write The bedrock was covered by talus than Talus covered the bedrock.

The best advice is: prefer the active voice, but do not eliminate the passive voice.

The passive voice is used where it is intended to stress the thing done rather than the doer, or when the doer is unknown: My hammer was broken stresses the breakage, whereas The assistant broke my hammer stresses the action of the assistant.