This is one of the difficulties of learning the English language. There are some patterns of word behaviour, but they may have to be pointed out even to English-speaking students. It may be necessary to indicate the error of a TV news correspondent who says the verb protest as if it were the noun protest.
That however is relatively easy, since there is an array of words that behave in the same way: record, conduct, object, subject, present, desert, contract, reject, escort, contrast, survey, rebel, insult, permit, increase… and so on.
But plenty of accentuation in English is beyond explanation: how for example do you explain to a visitor why we say St John’s Street, but St John’s Road? And then conventions of stress sometimes change for no apparent reason, and people accept the change. Twenty-five years ago, it was in the London Symphony Orchestra, but now it is becoming the London Symphony Orchestra.
Another trap for students—and sometimes their elders—is that body of words that are stressed on the first syllable, like communal, pastoral, lamentable, formidable, controversy, plethora.
There are oddities: did Byron and Swift pronounce it balcony? Yes. And why did some older, posh Roman Catholics pronounce it confession? And in The Tempest, the city is pronounced Milan.
Shakespeare can be cavalier about these things. In the first scene of A Midsummer Night’s Dream, Theseus says,
…but, O, methinks, how slow
This old moon wanes! she lingers my desires,
Like to a step-dame or a dowager
Long withering out a young man’s revenue.
But then, later in the scene, Lysander says to Hermia,
I have a widow aunt, a dowager
Of great revenue, and she hath no child.
How comfortable, and how convenient for students, that accentuation in Latin is so simple and so regular. If the penultimate syllable is long, it takes the stress; if it is short, the stress goes back to the syllable before:
amore, but tempore
verba Latina, but Carmina Burana
And pupils studying Italian or Spanish notice that these quantities and consequent stresses have usually been preserved.