When does + ing need double ending letters? It's said in the book that there is only one consonant at the end of the book, but why not use training? There's also playing and swimming. I'm going to faint again

When does + ing need double ending letters? It's said in the book that there is only one consonant at the end of the book, but why not use training? There's also playing and swimming. I'm going to faint again

It's said in the book that in the stressed closed syllable, there is only one consonant at the end of the syllable ing.rain It's not a closed syllable; play is not a closed syllable, but a vowel at the end