There are some words which even native English speakers can find confusing and on occasion get muddled. They may have very similar spellings or pronunciation or perhaps have very similar meanings.
Stationary and Stationery . The first refers to remaining still and the second to paper goods for writing.
Personnel and Personal. The first is often called Human Resources these days and refers to the staff and those who deal with them – those who engage and fire staff, those who deal with difficulties and arrange holiday rotas etc. The second is to do with what belongs to an individual; his personal affairs.
Nought and Naught. These both mean nothing, but the first refers specifically to the figure zero.
Then there are singulars and plurals. Do you know the plural of the words on the next page?