diff --git a/src/api/tcpip.c b/src/api/tcpip.c
index 6753fb82..4749b3d4 100644
--- a/src/api/tcpip.c
+++ b/src/api/tcpip.c
@@ -229,7 +229,7 @@ tcpip_callback_with_block(tcpip_callback_fn function, void *ctx, u8_t block)
 /**
  * call sys_timeout in tcpip_thread
  *
- * @param msec time in miliseconds for timeout
+ * @param msec time in milliseconds for timeout
  * @param h function to be called on timeout
  * @param arg argument to pass to timeout function h
  * @return ERR_MEM on memory error, ERR_OK otherwise
@@ -258,7 +258,7 @@ tcpip_timeout(u32_t msecs, sys_timeout_handler h, void *arg)
 /**
  * call sys_untimeout in tcpip_thread
  *
- * @param msec time in miliseconds for timeout
+ * @param msec time in milliseconds for timeout
  * @param h function to be called on timeout
  * @param arg argument to pass to timeout function h
  * @return ERR_MEM on memory error, ERR_OK otherwise
diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index 5065d31c..9363e2f9 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -261,9 +261,9 @@ err_t   netconn_gethostbyname(const char *name, ip_addr_t *addr);
 #define netconn_get_noautorecved(conn)        (((conn)->flags & NETCONN_FLAG_NO_AUTO_RECVED) != 0)
 
 #if LWIP_SO_RCVTIMEO
-/** Set the receive timeout in miliseconds */
+/** Set the receive timeout in milliseconds */
 #define netconn_set_recvtimeout(conn, timeout)      ((conn)->recv_timeout = (timeout))
-/** Get the receive timeout in miliseconds */
+/** Get the receive timeout in milliseconds */
 #define netconn_get_recvtimeout(conn)               ((conn)->recv_timeout)
 #endif /* LWIP_SO_RCVTIMEO */
 #if LWIP_SO_RCVBUF
diff --git a/src/include/lwip/sys.h b/src/include/lwip/sys.h
index 9791b864..018ff0ca 100644
--- a/src/include/lwip/sys.h
+++ b/src/include/lwip/sys.h
@@ -136,8 +136,8 @@ err_t sys_sem_new(sys_sem_t *sem, u8_t count);
 void sys_sem_signal(sys_sem_t *sem);
 /** Wait for a semaphore for the specified timeout
  * @param sem the semaphore to wait for
- * @param timeout timeout in miliseconds to wait (0 = wait forever)
- * @return time (in miliseconds) waited for the semaphore
+ * @param timeout timeout in milliseconds to wait (0 = wait forever)
+ * @return time (in milliseconds) waited for the semaphore
  *         or SYS_ARCH_TIMEOUT on timeout */
 u32_t sys_arch_sem_wait(sys_sem_t *sem, u32_t timeout);
 /** Delete a semaphore
@@ -178,8 +178,8 @@ err_t sys_mbox_trypost(sys_mbox_t *mbox, void *msg);
 /** Wait for a new message to arrive in the mbox
  * @param mbox mbox to get a message from
  * @param msg pointer where the message is stored
- * @param timeout maximum time (in miliseconds) to wait for a message
- * @return time (in miliseconds) waited for a message, may be 0 if not waited
+ * @param timeout maximum time (in milliseconds) to wait for a message
+ * @return time (in milliseconds) waited for a message, may be 0 if not waited
            or SYS_ARCH_TIMEOUT on timeout
  *         The returned time has to be accurate to prevent timer jitter! */
 u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout);
@@ -188,8 +188,8 @@ u32_t sys_arch_mbox_fetch(sys_mbox_t *mbox, void **msg, u32_t timeout);
 /** Wait for a new message to arrive in the mbox
  * @param mbox mbox to get a message from
  * @param msg pointer where the message is stored
- * @param timeout maximum time (in miliseconds) to wait for a message
- * @return 0 (miliseconds) if a message has been received
+ * @param timeout maximum time (in milliseconds) to wait for a message
+ * @return 0 (milliseconds) if a message has been received
  *         or SYS_MBOX_EMPTY if the mailbox is empty */
 u32_t sys_arch_mbox_tryfetch(sys_mbox_t *mbox, void **msg);
 #endif