Status Update: Upon discussion with an experienced member of the community who is currently teaching English, I have come to the conclusion that it may not be possible to present any single system of classifying the tenses as being a "basic" or "standard" model.
There seems to be a lack of consensus on having a definitive system even at the elementary school/new ESL learner level, not just among linguistics scholars. Supporting this observation: http://random-idea-english.blogspot.com/2014/01/a-brief-history-of-tense.html
Given this consideration, I'm considering abandoning this topic for a Canonical Post as "inherently opinion based," and closing this Meta question.I have voted to close this question as "Opinion-Based."
Reason: It wouldn't be correct to present any one model as being definitive/universal if it isn't, but the alternative would be a discussion and comparison among many different models (along the lines of the original CP proposal before editing). This was considered to be not a good fit for this site.
I'm only waiting for a final verdict from one of the other contributors before close-voting this.
Thank you to everyone who has invested their time and attention in this discussion. I would be open to contributing to the CP project on a different topic if an alternative is proposed by the community.
Edit: This has been significantly revised - see the edit history and the discussion in the comments. Instead of an overview and comparison of the different models in use to describe the tense system in English, the focus has been shifted to explaining the details of the most basic model. In its original form, this CP proposal was thought to be too opinion-based or likely to generate off-topic discussion.
PROPOSED CANONICAL POST - SUGGESTIONS FOR IMPROVEMENT ARE WELCOME!
TENSE AND ASPECT
- What tenses exist in English? How many are there?
That depends on how you define tense! For now, let's stick with the simplest definition. This is the one most native speakers learn in school, and also the one you are most likely to see if you're new to learning English. Tense is defined by the Merriam-Webster online dictionary as "a distinction of form in a verb to express distinctions of time or duration of the action or state it denotes."
First, let's look at the "distinctions of form" which "express distinctions of time." Using "categorize" as an example, here are each of the 6 distinct tenses that exist in English:
| Present | They categorize |
| Past | They categorized |
| Future | They will categorize* |
| (Present) Perfect | They have categorized |
| Past Perfect [also called Pluperfect] | They had categorized |
| Future Perfect | They will have categorized |
This post on ELU has a helpful chart showing how the different tenses fit into the timeline.
*Adding the helping verb "will" is the most basic way of indicating the future tense. In actual conversation, however, you're as likely or more likely to hear future actions described with a construction like "going to categorize" or "about to categorize" instead of "will categorize." Sometimes, just the present continuous on its own can be used to refer to the future, when the meaning is clear from the context. You can see some examples of this here: How to say that you have plans to go to the movies tonight? and here: When to use "be going to" / present continuous in future?
- What is "aspect"?
Each tense has 2 variants--the Simple and the Progressive/Continuous--which are called aspects.
The characteristic of aspect adds more detail to the time information given by the tense: information about "the duration of the action or state" the verb "denotes."
The word "tense" is sometimes used to describe the combination of a tense plus an aspect. For example, you might hear about the "Simple Present Tense" or the "Past Continuous Tense."
Combining the two aspects with the six tenses listed above gives a total of 12 different possibilities.** This time, we'll demonstrate these with the verb "sit," because it has fewer letters:
| Simple | Continuous | |
|---|---|---|
| Present | They sit | They are sitting |
| Past | They sat | They were sitting |
| Future | They will sit | They will be sitting |
| Perfect | They have sat | They have been sitting |
| Past Perfect | They had sat | They had been sitting |
| Future Perfect | They will have sat | They will have been sitting |
**Sometimes you'll hear about there being 12 tenses in English, instead of 6. If your teacher or textbook talks about the 12 tenses, they are most likely referring to the 12 combinations of tense and aspect.
- What about tense and aspect for non-finite forms?
Non-finite forms (the infinitive, participle, and gerund) also have tense and aspect, but they only have two different possibilities for tense (present and perfect) instead of the six that finite verbs have.
| Simple Present | Present Continuous | Simple Perfect | Perfect Continuous | |
|---|---|---|---|---|
| Infinitive | to sit | to be sitting | to have sat | to have been sitting |
| Participle | N/A | sitting | having sat | having been sitting |
| Gerund | N/A | sitting | having sat | having been sitting |
What tense to use for the non-finite forms is determined by their time reference relative to the main verb in the sentence.
If the action of the non-finite form happens at the same time as that of the main verb, use a present form:
- "Alice is known to like apples and oranges." The time reference of the action described by the infinitive "to like" is the same as that of the main verb "is known": both present.
- "Sitting on the bench, Bob saw a seagull." Bob's seeing the seagull happens at the same time as his sitting - both in the past.
- "Rover's barking at a squirrel startled the seagull." The main verb "startled" is in the simple past tense. The dog's barking coincides with the seagull being startled (i.e. the two actions happen in the same timeframe), so even though the sentence describes cause and effect, the tense of "barking" should be present, not perfect.
If the action of the non-finite form happens before that of the main verb, use a perfect form:
- "Carol is known to have been baking cupcakes all morning for the fundraiser." The time reference of the action described by the infinitive "to have been baking" is earlier than that of the main verb "is known": the action of "baking" happened in the past, while "is known" refers to the present. Note the use of a continuous aspect for the perfect infinitive, as it describes an action occurring over a period of time.
- "Having sat on the bench, Dan knows it's uncomfortable." The action indicated by "having sat" happened sometime in the past, while the main verb "knows" refers to the present time.
- "Evan will arrive at school late due to having overslept." "Having overslept" refers to an action in the past, while "will arrive" refers to the future, so the gerund is perfect tense in this sentence.
