Fiancée's Age Joke (With Grammar Explanations)

你的未婚夫知道你的年龄吗？ 
nǐ de wèi hūn fū zhī dào nǐ de nián líng ma
Does you fiance know your age? 

是的，他知道一部分。 
shì de tā zhī dào yī bù fèn 
Yes, partly.

Grammar Explanations

Expressing Possession Using 的

In Chinese language, the particle 的 (de) is widely used to express possession. The following pattern is simple but truly universal. A good news is that you don't need to memorize separate words for possessive pronouns. They are composed by adding 的 to a personal pronoun: 

Noun 1 (Pronoun) + 的 (de) + Noun 2 

妈妈的杯子 - mā mā de bēi zi - Mom's cup 
爸爸的书 - bà ba de shū - Dad's book 
你的未婚夫 - nǐ de wèi hūn fū - your fiance 
你的年龄 - nǐ de nián líng - your age 

When talking about close personal or organizational relationaship, 的 (de) should be omitted. The following collocations sound more natural without 的: 

我女朋友 - wǒ nǚ péng yǒu - my girlfriend 
他公司 - tā gōng sī - his company 
她家 - tā jiā - her home 
你姐姐 - nǐ jiě jiě - your elder sister

"Partly", "The Most Part", "Vast Majority"

一部分 (yī bù fen) stands for "partly". It is literally translated as "one part". 
By replacing 一 (one) with 大 (big), you get another meaning: 
大部分 - dà bù fen - the most part, the greater part, the majority of 
大部分 has a synonym: 
大多数 - dà duō shù - vast majority