Many nouns form their plural with s, but some have irregular plurals. Use a or an only with singular nouns. Do not say a books.
Practical examples
One ticket, two tickets.
تذكرة واحدة، تذكرتان.
One person, three people.
شخص واحد، ثلاثة أشخاص.
There are four boxes here.
توجد أربعة صناديق هنا.