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+# nng_duration
+
+## NAME
+
+nng_duration --- relative time in milliseconds
+
+## SYNOPSIS
+
+```c
+#include <nng/nng.h>
+
+typedef int32_t nng_duration;
+
+#define NNG_DURATION_INFINITE (-1)
+#define NNG_DURATION_DEFAULT  (-2)
+#define NNG_DURATION_ZERO     (0)
+```
+
+## DESCRIPTION
+
+An {{i:`nng_duration`}}{{hi:duration}} is a relative time, measured in {{i:milliseconds}}.
+This type is most often used in conjunction with timers and timeouts.
+
+A couple of special values have been set aside, and carry special meanings.
+
+- {{i:`NNG_DURATION_DEFAULT`}}:
+  Indicates a context-specific default value should be used.
+
+- {{i:`NNG_DURATION_INFINITE`}}:
+  Effectively an infinite duration; used most often to disable timeouts.
+
+- {{i:`NNG_DURATION_ZERO`}}:
+  Zero length duration; used to perform an immediate poll.