.I seconds\fR\fB;\fR
.PP
IPv6 addresses have \'valid\' and \'preferred\' lifetimes. The valid lifetime
-determines at what point at lease might be said to have expired, and is no
+determines at what point a lease might be said to have expired, and is no
longer useable. A preferred lifetime is an advisory condition to help
applications move off of the address and onto currently valid addresses
(should there still be any open TCP sockets or similar).