diff -r a29c5c35951b -r 045ff80b6455 data/dictionary.xml
--- a/data/dictionary.xml	Tue Aug 13 18:00:06 2013 +0200
+++ b/data/dictionary.xml	Tue Aug 13 20:31:34 2013 +0200
@@ -1612,7 +1612,15 @@
 	</concept>
 	<concept>
 		<term abbreviation="MAC" completeForm="media access control" language="en"/>
-		<explanation language="en"><text></text></explanation>
+		<explanation language="en">
+			<text>
+				a data communication protocol, a sublayer of the layer 2 in OSI model (data link layer); 
+				a MAC address is a unique identifier of an network interface – used for IEEE 802 networks including Ethernet;
+				they are assigned by the manufacturer of the card and stored in the hardware (can be often changed by the software);
+				there are three numbering namespaces: MAC-48, EUI-48 and EUI-64;
+				the address has 6 or 8 bytes and they are usually written in HEX, octets separated by : (a colon)
+			</text>
+		</explanation>
 		<tag>computer</tag>
 	</concept>
 	<concept>