Learn Hardcore Swahili: Ili kuepuka kuanguka, ni lazima tuchukue tahadhari wakati tunapanda ngazi. - In order to avoid falling, we must take caution when climbing the stairs.

ili is a conjunction that introduces a purpose clause, equivalent to English “in order to” or “so that.” In this sentence it signals why we must act:
• ili kuepuka kuanguka = “in order to avoid falling.”
You can also place the ili‐clause after the main clause (e.g. “Ni lazima tuchukue tahadhari… ili kuepuka kuanguka”) without changing the meaning.

Why do we see kuepuka kuanguka with two ku prefixes?

Each verb in Swahili uses ku- to form the infinitive (to-verb). Here you have two verbs:

kuepuka = “to avoid” (ku + pue + ka)
kuanguka = “to fall” (ku + anguka)
Together they literally read “to avoid to fall,” which we render naturally as “to avoid falling.”

What does ni lazima mean? Could I use inabidi instead?

ni lazima means “it is necessary” or “one must.” It’s a fixed construction of the copula ni + noun lazima. You can indeed replace it with inabidi, which also takes the subjunctive afterward:
• Ni lazima tuchukue…
• Inabidi tuchukue…
Both express obligation, but some regions or registers prefer one over the other.

Why is the verb tuchukue in the subjunctive mood?

Expressions of necessity or obligation (like ni lazima, inabidi) require the following verb to be in the subjunctive. The subjunctive in first‐person‐plural is formed as:
• tu- (we) + chuk- (root “take”) + -ue (subjunctive ending) = tuchukue.

What is the role of the prefix tu- in tuchukue and tunapanda?

The prefix tu- marks the subject “we.”
• In tuchukue, tu- + root + subjunctive ending => “let us take.”
• In tunapanda, tu- + -na- (present continuous marker) + root => “we are climbing.”

Why does tunapanda use the continuous aspect marker -na- even though it’s introduced by wakati (“when”)?

With time‐clauses introduced by wakati, Swahili normally uses the habitual or continuous aspect to show an action happening at that time. Hence tunapanda = “we are climbing/whenever we climb,” not the subjunctive. If you wanted a hypothetical “if we were to climb,” you’d choose a different structure, but here it’s a real, ongoing action.

Why is the purpose clause placed before the main clause? Can I switch their order?

Swahili word order is relatively flexible. Placing ili kuepuka kuanguka first foregrounds the purpose. You can switch them without changing meaning:
“Ni lazima tuchukue tahadhari wakati tunapanda ngazi ili kuepuka kuanguka.”
Just mind your punctuation (commas) to keep the sentence clear.

What noun class is ngazi, and does it affect any agreement here?

ngazi (“ladder” or “step”) belongs to noun class 9/10, which typically has no explicit prefix in singular and plural. In this sentence it stands alone as the object of tunapanda, so there’s no adjective or demonstrative to agree with. If you added one, you’d use the class 9 concord (e.g. ng’azi hii = “this ladder/step”).