Which verb features are commonly marked in Nilo-Saharan languages?

In Nilo-Saharan languages, the verb is typically the most complex grammatical component. These languages frequently utilize extensive marking for the following conjugational and inflectional features:

• Person and Number: Specific inflectional markers are common, such as the prefix a- for the first person singular and i- for the second person singular.1
• Tense and Aspect: Verbs are marked to express time (tense) and aspect, with a widespread distinction between perfective and imperfective stems found across diverse groups like the Saharan, Taman, Nyimang, and Surmic languages.1
• Voice and Derivation: Markers for causative, dative, and negation are frequently used and often share similar forms across the language family.1

These morphological processes are often accompanied by consonant mutation. Many of these verbal features are considered retentions from a common ancestral language.1