Learn Farsi: در هنر صحافی، یک لغزش نیز پذیرفتنی نیست. - In the art of bookbinding, not even one slip is acceptable.

In affirmative sentences, نیز does mean 'also' or 'too'. However, when you use the pattern یک (one) + noun + نیز combined with a negative verb like نیست, it creates an emphatic scalar negation. Literally it means 'one slip also isn't...', which translates naturally into English as 'not even one slip is...'.

Could I use هم instead of نیز to create this emphatic negation?

Yes, absolutely! یک لغزش هم پذیرفتنی نیست means exactly the same thing. The difference is purely about register: نیز is more formal and literary, which suits the slightly elevated tone of discussing a specialized craft like bookbinding. In everyday speech, you would almost always use هم.

How is the adjective پذیرفتنی (acceptable) built?

It is formed by taking the past stem of the verb پذیرفتن (to accept) and adding the suffix ـنی (-ani). This very productive suffix attaches to past stems to create adjectives meaning 'capable of' or 'worthy of' an action, similar to دیدنی (worth seeing) or خوردنی (edible).

Is لغزش only used for physical slipping?

No, while it comes from the verb لغزیدن (to slip or slide), لغزش is frequently used metaphorically. In contexts like this, it means a 'mistake', 'lapse', or 'error', much like how we say 'a slip-up' or 'a slip of the tongue' in English.