Modal Verbs – Should
“Should” is used for suggestions and recommendations.
When using “should” as a suggestion the structure is as follows:
The negative of “should” is “should not“, but we use the contracted form of “should not” (shouldn’t) more frequently.
The structure for “shouldn’t” is the same as it is for “should”.
Subject + Shouldn’t + Verb in Infinitive Form + Complementizer
“Should” is also used as a strong possibility because usually the speaker has a reason or some evidence for making the statement.
In the above examples the speaker has reasons or evidence for believing what they are saying. The possibility when using “should” is a little more stronger when using “might” or “may” because the speaker is a little more certain of the situation because there is more evidence in the above situations.
The formula for using “should” as a strong possibility is the same as it is for “should” as a suggestion:
Subject + Should + Verb in Infinitive Form + Complementizer
The negative form is the same as well, that is we use the contracted form, “shouldn’t” much more frequently than “should not“.