-zo-

To become confident with the Class 10 relative -zo-, you need to understand where it attaches and its specific rules:

1. Infixed inside the verb
The most common way to use -zo- is to place it directly after the tense marker. However, this is strictly limited to three tenses and one negative marker:

• Present (-na-): zinazo...
• Past (-li-): zilizo... (Note: There is also a defective verb root -li meaning 'to be' which is used as a present-tense relative copula, so zilizo alone means 'which are', e.g., nguo zilizo safi)
• Future (-taka-): zitakazo... (Note that -ta- must change to -taka-)
• Negative (-si-): zisizo... (This is a tenseless negative marker, not a tense)

2. The amba- strategy
If you want to use a tense that cannot take an infix (most notably the perfect tense -me-), you must use the independent word ambazo. For example, you cannot say *zimezoanguka; you must say ambazo zimeanguka. However, ambazo is also a universal alternative that can be used with ANY tense (e.g., ambazo zinaanguka is just as valid as zinazoanguka). Furthermore, to express specific negative past or future tenses, you must use ambazo with the corresponding negative tense (e.g., ambazo hazikuanguka 'which did not fall', ambazo hazitaanguka 'which will not fall').

3. The General (Tenseless) Relative Suffix
For habitual actions or general facts, the relative marker can be attached as a suffix to the end of the verb, with no tense marker used. For example, nguo zifaazo ('clothes which are suitable').

4. Object Relatives
When the Class 10 noun is the object of the relative clause (e.g., 'the clothes which I bought'), you will often see the relative -zo- right next to the object marker -zi-. For example: nguo nilizo-zi-nunua. Do not confuse the two; -zo- means 'which', and -zi- means 'them'. Note the structural difference: in a Subject Relative, both the subject prefix and the relative infix match the noun (e.g., zi-na-zo-anguka), whereas in an Object Relative, the subject prefix belongs to the doer, and only the infix matches the Class 10 noun (e.g., ni-li-zo-nunua). Because any noun that triggers the Class 10 -zo- agreement is grammatically inanimate, the object marker is optional. It is highly common and perfectly correct to drop the -zi- entirely (e.g., nguo nilizonunua).

5. Relative Possession ('which have')
Because Swahili expresses 'to have' as 'to be with', you combine the relative copula -li- with na to form zilizo na (e.g., nguo zilizo na madoa 'clothes which have stains').

6. Emphatic Copula (ndizo) and Negative (sizo)
When attached to the prefix ndi-, it forms the emphatic copula ndizo ('they are the ones which' or 'those are exactly the ones'). Its negative counterpart is sizo ('they are not the ones').

7. The Animate Exception
Remember that animate nouns in Class 10 (like mbwa 'dogs' or kuku 'chickens') take Class 2 human/animate agreement. Therefore, 'the dogs which are sleeping' is mbwa wanaolala, not *mbwa zinazolala.