An interjection is usually a short word(sign) in South African Sign Language that expresses strong emotion, agreement, disagreement or surprise; it functions independently in a sentence. An interjection in SASL like in English can be placed(interject) anywhere in a conversation. Even while the person is busy signing you could reply or interject with an interjection to acknowledge, agree or disagree.
A few examples of interjections:
Some interjections are fingerspelled such as O-K (okay).
Non-manual features and facial expressions are necessary when using interjections.