The Present Perfect Simple Tense

When there is a connection either action and/or result from the past to the present time, we use the Present Perfect Tense.

The present perfect simple is formed with "have/has + past participle".

 It is used for:

1. an action you did in the past but wish not to mention the specific time.

• Have you done your homework yet? ~ Yes, I have. / No, I haven't.
• I have finished the project that you gave me. (Maybe you have forgotten when you finished it or maybe you do not want to tell when you finished it.)
• I have lost my phone. (You do not know the exact time you lost it)

In this case, it is used to talk about:

Experiences:

• I have been to Paris.
• I have never loved anyone.

Changes:

• You have changed a lot since we met last year.
• My English has improved since I moved to this school.
• The bus fee has gone up rapidly.

Accomplishments:

•  They have won a lot of games in the past few years.
• My daughter has learned how to sing.

Uncompleted actions you are supposed to have done (with "yet" in negative sentences):

• I haven't bought the milk yet.
• The teacher hasn't returned us the quiz result yet.

Repeated actions at different time:

• I have been to Paris four times this year.
• We have met a lot of famous people recently.

Used with "yet" to ask if someone has completed a task:

• Have you done the washing yet? ~ Yes, I have. / No, I haven't.
• Has he watched that movie yet? ~ Yes, she has. / No, she hasn't.
• Has the teacher check the attendance yet? ~ Yes, he has. / No, he hasn't.

An action which was completed earlier than expected. (with "already" in positive sentences):

• Can you go to the market and get some oil? ~ I have already bought some.
• Don't forget to water the flowers. ~ No worry. I have already asked Jane to do it.

2. We also use the present perfect simple tense to talk about continuation in the present (an action that happened in the past and continues until now with "for" (a period of time until now" and "since (from a specific time in the past until now")

• I have learned English for 3 years.
• She has worked as a waitress for 6 weeks and now she's tired of it.
• They have stayed in that village since October.

The Simple Past Tense

The Simple Past tense is used to express a completed action in a definite time before now (either a recent completed action or a distant completed one). For this reason, speakers always attach a specific past time expression or phrases in the simple past tense.

1. She needed a lot of help last week.
2. I ate a lot candy when I was young.
3. The electricity was off the whole night last night.
4. Four years ago, we didn't have specific plans for our business.

The past tense verb forms differ from the present verb forms.

1. I go to school by bus. (present simple)
   Yesterday, I went to school by bus. (past simple)
2. He does his homework after dinner. (present simple)
   He did his homework after dinner last night. (past simple)
3. They need some help. (present simple)
   They needed some help a few days ago. (past simple)

Forms of the Simple Past 

Positive Form

Unlike the present simple tense, the past simple verb is used with all subjects without any changes.

Negative Form

The auxiliary verb "did" + "not" is used with the base form of the main verb in order to form the simple past tense form.

Question Form

In the question form, the auxiliary verb "did" is placed before the subject pronoun together the base form of the main verb to form questions.

Answering to the questions:

• Yes, [subject] did.
• No, [subject] didn't. (not "did not")

The Present Simple Tense

 Uses of the present simple tense:

1. to express your habits
1. They watch TV every night.
2. I get up at 7 o'clock.
3. I have my breakfast at 8 o'clock.
2. to express your routines / repeated actions or activities
1. They fly to Japan every summer holiday.
2. It rains every morning in the winter.
3. I always go to school by bus.
4. He never forgets to do his homework.
5. I drive to Siem Reap once a year.
3. to express general truths or facts
1. Water boils at 100 degree Celsius.
2. The sun rises from the east and sets at the west. 
3. Water freezes at 0 decree Celsius.
4. Money doesn't guarantee happiness.
5. It is the biggest house in the village.
4. to express scheduled future activities or events. The verbs which are generally used in this situation are: arrive, be, begin, close, depart, end, finish, fly, leave, open, start, get, go, have, return.
   
1. I fly to New York tomorrow.
2. The bank opens at 9.00 and closes at 4.00.
3. The train to Sihanouk Ville leaves at 10 AM. 
4. The meeting starts at 3 AM.
5. What time does the train leave?
5. to be used after conjunctions of time (as, before, until, when, while, as soon as, after, since, once) to express future happenings.
1. I'm not going to sign this contract until it is signed by the other party first.
2. Look both ways when you cross the street.
3. I always brush my teeth before I go to bed.
4. We will go as soon as the rain stops.
6. to give instructions, directions, and orders (imperatives)
1. Don't go there alone.
2. Brush your teeth before you go to bed.
3. Stay here.
4. Shut up.
5. First, open the box. Then, take it out...
7. to be used in the news headline. The events finished, but to attract readers' attention of the events, the present simple is used in the active voice.
1. Trump wins presidential election.
2. Japan agrees aid for port expansion
3. Minister aims to boost farming through partnerships.

Forms of the present simple tense

The Positive Form

We notice that all the third person singular subjects (he/she/it/singular subject) have suffixes -s and -es at the end of each main verb. Note below on how to add suffixes to the third person singular:
1. We add -s to most verbs:

• talk - talks
• sing - sings
• leave - leaves
• swim - swims
• ring - rings

2. With verbs ending in -s, -ss, -ch, -sh, -o, -x, and -z we add -es to the verb.

• teach - teaches
• box - boxes
• fix - fixes
• kiss - kisses
• wish - wishes
• go - goes
• do - does

3. With verbs ending in "consonant + y", we change the -y to -i and add -es.

• cry - cries
• carry - carries
• deny - denies
• fly - flies
• hurry - hurries
• reply - replies
• study - studies
• worry - worries

But we do not follow the above rule if the form is "vowel + y":

• stay - stays
• play - plays
• betray - betrays
• decay - decays

The Negative Form

In negative form, the main verb does not take -s or -es, but the auxiliary verb "do/does" + "not" is placed before the main verb.

The Question Form

Yes/No Questions

The auxiliary verb do/does is placed before the subject while the main verb is in the base form of the verb in the question form. 

In order to answer a yes'/no question, only the subject and the auxiliary verb are used.

• Yes, I/we/you/they do. / Yes, he/she/it does.
• No, I/we/you/they don't. / No, he/she/it doesn't. (not "do not" or "does not")