The term **'zk'** commonly stands for **zero-knowledge** in the context of cryptography. It refers to a method by which one party (the prover) can prove to another party (the verifier) that a statement is true without revealing any information beyond the fact that the statement is indeed true. Examples include **zk-SNARKs** (Zero-Knowledge Succinct Non-Interactive Argument of Knowledge) and **zk-STARKs** (Zero-Knowledge Scalable Transparent Argument of Knowledge), which are used in blockchain technology to provide privacy and scalability.