All and Every

All and every can have the same meaning but all is used with a plural noun as in All towns have a post office, and every is used with a singular noun as in Every town has a post office. Similarly , in the negative, " not all" is used with a plural noun and "not every" with a singular noun ,as in Not all towns have/ Not every town has a hospital.

Allow and let

Allow is more formal than let. Allow is used with an object and an infinitive verb with "to".

Allow mike go home.

Let is used with an object and an infinitive verb without "to".

Let  mike go home.

Let has no passive form. Use allow as “in be allowed to go home”.

Permit is more formal than allow.

Also, As well and too

Also is placed near the verb as in I would also like to go. As well and too can be placed at the end of a clause as in I would like to go on a trip to India as well/too.

Also is preferred when referring to the verb, as in I can also swim (in addition to doing other activities) and "too" is preferred when referring to the subject, as in I, too, can swim (in addition to other people). Also, as well and too cannot be used in negative sentences.

In and At

In is used for large or important places (e.g. A country and city) and for

Structures, objects, situations etc that have, or seem to have length, depth and height (e.g. buildings, vehicles,  containers, books,  a group of people). At is only possible when referring to a place (esp a building ) when being physically inside is not absolutely necessary, as in at the station / library.

Note also that "at school" can mean being a pupil. As in My son's still at school , as well as referring to where a person is, as in She’ll be at work until 6 o’clock and "in work" means employed as in She hasn’t been in work for months.

Murder and kill

Murder is used when a person's death is planned and caused by another person.

She was murdered by her husband.

He was killed in a car accident.

Persons and people

Persons is the standard plural of person but is only used in formal situations, as in Persons under 16 may not enter. In usual contexts use  people as in Six people came.

Say and Tell

Say is almost always followed by an object that is not a person.

 We say something.

Tell is usually followed by an object that is a person.

 We tell someone something.