should and ought to intechangeable

[ostap77]

I've looked it up in an Grammar text book here is what it says:

Should and ought to both express advisability or suggestion and the two are interchangeable
in meaning. Some grammarians consider only should a pure modal and
argue that ought to be classified as a related structure. Regardless of how they are
classified, should and ought to are closely related semantically and generally taught
together in ESL/EFL texts. Ought to occurs less frequently in American English
than should, although there are regional variations.
Questions and negatives with should and ought to follow the first auxiliary rule.
However, in American English, not is rarely used with ought to, nor is ought to
generally used in questions.
Learner difficulties
In spoken speech, ought to is generally reduced and sounds like outta or
oughta, and may be written as such in dialogues to reflect spoken speech.
In its reduced form ought to (outta/oughta) can be considered more informal
than should.

"Tiller clutched Sairy’s arm as they followed Dallas. Florida trailed
them, kicking at rocks and tree trunks as she went. “Oughta just run
away right now,” Florida mumbled. “Oughta just bury us alive."

What do you think about it?

"You’re late.
You should have left earlier.
You ought to have left earlier."

[5jj]

"Should and ought to both express advisability or suggestion and the two are interchangeable in meaning".

I am not very happy about interchangeable in meaning. If it means that both words express advisability or suggestion, and the speaker is free to choose either, then that is largely true.

Don't forget, however, that, should can be used in situations where there is no idea of advisability or suggestion, and ought to is not possible, for example:

If I should die, think only this of me...
Should you require anything else, just call me.

My usual advice to students is: "Always use should. In some circumstances some native speakers might use ought to, but should is always correct".

[ostap77]

"Should and ought to both express advisability or suggestion and the two are interchangeable in meaning".

I am not very happy about interchangeable in meaning. If it means that both words express advisability or suggestion, and the speaker is free to choose either, then that is largely true.

Don't forget, however, that, should can be used in situations where there is no idea of advisability or suggestion, and ought to is not possible, for example:

If I should die, think only this of me...
Should you require anything else, just call me.

My usual advice to students is: "Always use should. In some circumstances some native speakers might use ought to, but should is always correct".

In your examples yes.

"You should have learned these words."

OR

"You ought to have learned these words."

I guess for a speaker there would not be a difference.

[lauralie2]

In your examples yes.

"You should have learned these words."

OR

"You ought to have learned these words."

I guess for a speaker there would not be a difference.

Of the two, "should" is the more common, and while both "should" and "ought to" mean it's advisable, "ought to", to me at least, also means a moral obligation:

• You should/ought to go to work. <it's advisable>
• You ought to go to work. <you are morally obligated>

And so, the second example below sounds awkward to me:

• You ought to have learned those words. <advisable>
• You ought to have learned those words. <you are morally obligation>