Mastering verb usage is extremely important in conquering the verbal portion of the GMAT. Here is a detailed primer on tense:

A. Time

"Tense" tells about time. That is, a verb's tense indicates when the action specified by the verb took place. An action or event can take place in the past, the present, or the future.

1. Present

Verbs in the present tense indicate an action that is taking place right now, in the present moment only. Present tense verbs can also indicate unchanging states of being or action, or repeated actions:

I am happy right now.

Here, the present tense verb am indicates something happening right now: the speaker is happy at this present moment in time.

I am a happy person.

In this sentence, the present tense verb am indicates an unchanging state: the speaker is generally a happy person, or that his state of being is one of unchanging happiness.

I study Greek for two hours every day.

Here, the present tense verb study indicates a repeated action: the speaker studies once a day, every day.

Present tense verbs are formed by taking the uninflected (unaltered) form of the verb, which is found by removing "to" from the infinitive form: for example, the present tense walk from the infinitive to walk, the present tense talk from the infinitive to talk, or the present tense eat from the infinitive to eat.

2. Past

Verbs in the past tense indicate an action that took place in the past: that is, at some point prior to the present moment.

Yesterday, I walked to the store.

Here, the past tense verb walked indicates an action that took place yesterday, and is no longer happening.

Past tense verbs are usually formed by adding an –ed to the uninflected (or present tense) form of the verb: for example, talk becomes talked, walk becomes walked and balk becomes balked. (Irregular verbs, such as to eat and to have, are not formed in the same way; if you are unfamiliar with these forms, consult a basic English grammar guide.)

3. Future

Verbs in the future tense indicate an action that takes place in the future: that is, at some point after the present moment.

Tomorrow, I will eat dinner with friends.

Here, the future tense verb will eat indicates an action that will occur, in its completion, tomorrow.

Future tense verbs are usually formed by adding will or shall to the uninflected (or present tense) form of the verb: for example, talk becomes will talk or shall talk, walk becomes will walk or shall walk, eat becomes will eat or shall eat.

B. Aspect

In addition to an event's place in time, verb forms can also indicate how long the event continued, or for what duration it occurred. "Aspect" describes the event's completion, duration, or repetition: did the event happen only once, in the past? Or, did it begin to happen in the past, and still happening? Or, will it happen, and continue to happen for some time, at some later time? Or, does it happen every so often, but not continuously?

Each basic tense (past, present, future) has a perfect, progressive, and perfect progressive forms:

1. The perfect form indicates an action that is completed.

Past Perfect is used to describe events or activities that took place in the past, before another event or action. The past perfect is formed by adding had to the past participle form of the verb, which usually ends in -ed:

By the time Michael arrived, the party had ended.

Present Perfect is used to describe events or activities that were begun in the past. The present perfect is formed by adding has or have to the past participle form, which usually ends in –ed:

I have played the game.

Future Perfect is used to describe events or activities that will begin at some point in the future, before another event or activity. The future perfect is formed by adding will have to the past participle form, which usually ends in –ed:

Michael is always late. By the time he arrives tonight, the party will have ended.

2. The progressive form indicates an action that is ongoing.

Past Progressive is used to describe an event or activity that was occurring when a second event or activity occurred. The past progressive is formed by using was or were with the form of the verb that ends in –ing:

We were playing basketball when the car smashed through the gate.

Present Progressive is used to describe an event or activity that is happening currently: at the moment the sentence is written. The present progressive is formed by adding am, is, or are to the form of the verb that ends in –ing:

We are eating dinner right now.

Future Progressive is used to describe an event or activity that will occur in the future, and will continue to happen for an extended period of time. The future progressive is formed by adding will be or shall be to the form of the verb that ends in –ing:

For the next several months, Michelle will be traveling through Europe.

3. The perfect progressive form indicates an action that is ongoing, but will be completed at some definite time.

I have been studying.

4. PRONOUN AGREEMENT

B. Verb Tense