Halb vs. Hälfte
While both halb and Hälfte translate to "half" in English, they serve different grammatical functions. halb is primarily an adjective describing a quality or measurement, while Hälfte is a noun referring to a specific part or quantity of a whole.
Halb
A1This word functions as an adjective or adverb. It is used to describe a noun as being "half a..." something, to indicate time, or to express a state of being half-done. When appearing before a noun, it changes its ending based on grammatical gender and case.
Ich habe nur ein halbes Glas Wasser getrunken.
(I only drank half a glass of water.)
Wir treffen uns um halb drei am Bahnhof.
(We are meeting at half past two at the train station.)
Die Flasche ist noch halb voll.
(The bottle is still half full.)
Er hat eine halbe Stunde auf den Bus gewartet.
(He waited half an hour for the bus.)
Das ist doch nur die halbe Wahrheit.
(That is only half the truth.)
Hälfte
A2This is a feminine noun (die Hälfte) and must always be capitalized. It refers to "the half" as a concrete object, section, or mathematical fraction. It is frequently followed by an of construction (genitive case) to specify what it is half of.
Bitte schneide den Kuchen in zwei Teile und gib mir die Hälfte.
(Please cut the cake in two parts and give me the half.)
Die erste Hälfte des Spiels war sehr spannend.
(The first half of the game was very exciting.)
Er hat mehr als die Hälfte seines Geldes ausgegeben.
(He spent more than half of his money.)
Meine bessere Hälfte ist heute leider nicht dabei.
(My better half is unfortunately not here today.)
Fast die Hälfte der Angestellten kommt mit dem Auto.
(Almost half of the employees come by car.)
Summary
Use halb as a descriptive word (adjective) when saying "half a [thing]" or telling time. Use Hälfte as a noun when you are talking about "the half" as a distinctive piece or portion of a larger whole.