Families in America are currently categorized into threes types according to their structure:
Nuclear family 
Single-parent
Extended family
Nuclear family 
The nuclear family is considered the "traditional" family. The nuclear family consists of a mother, father, and the children. The two-parent nuclear family has become less prevalent, and alternative family forms have become more common. These include homosexual relationships, single-parent households, and adopting individuals. The nuclear family is also choosing to have fewer children then in the past. The percentage of married-couple households with children under 18 has declined to 23.5% of all households in 2000 from 25.6% in 1990, and from 45% in 1960 
Single-parent
A single-parent (also termed lone parent or sole parent) is a parent who cares for one or more children without the assistance of the other biological parent. Single-parent homes are increasing more and more as married couples divorce, or as unexpected pre-marital pregnancies occur. The percentage of single-parent households has doubled in the last three decades, but that percentage tripled between 1900 and 1950. The sense of marriage as a "permanent" institution has been weakened, allowing individuals to consider leaving marriages more readily then they may have in the past.
Extended family
The extended family consists of grandparents, aunts, uncles, and cousins. In some circumstances, the extended family comes to live either with or in place of a member of the nuclear family. An example includes elderly parents who move in with their children due to old age. This places large demands on the caregivers, particularly the female relatives who choose to perform these duties for their extended family.

Michael:Hi! I saw you last Monday. We register together, remember? I’m Michael.
Jane: Hi, I’m Johnny. Lucky to see you again. This is Lily, my classmate.
Lily: Nice to make your acquaintance .Would you like to join us?
M :Of course. I guess you are leaving for the freshman’s lectures, so do i.
J:Yes,so,how are things going?
M:Pretty good, but school has been really hectic since i came in. I haven’t even had a chance to breathe!
L : Me too, you can’t believe how much work we have to finish to get ready for classes. It’s can’t be more complex.
J : It’s always especially crazy for freshman. hey, what’s your major?
M: Travel and tourism ,you surely know that!
J:I think this major should be one in great demand. We study in mathematics.
M:wow, You must very clever.
J: Thanks, but I choose that one just because i have a huge interest in math. 
L:Well,jane want to be a scholar. She really deserve it, does not she? Explicit target is so significant. what do you plan to do after graduation?
M: uh...I am not yet decided. I’d like to work for a travel agency in this area. what about you?
L: Well. When i first started college, I majored in physics but later I realized i might have a hard time finding a job in that field. I ended up changing to Jane’s major. Finding a job in a wider area should be much easier.
J:Programming is a good job. i think you will find it very interesting. they can make a program or a web, enriching our life.
L:You are right, I can’t agree more.
M:Have you got a part-time job to support yourself though school, lily?
L :Well.I am on a four-year scholarship that pays my tuition.
M:Well.lucky you .
J:And you? are you paying for school yourself?
M:Sort of. I work weekends at a travel agency.
J:Sounds great!
L:A travel agency? That seems like a perfect experience for you? What do you do there?
M:I am a tour guide. I show tour groups around the city.
J:wow, your English must be pretty good then.
M:Actually they’re all Chinese tourists. That’s why i got the job.
L:oh,here we are. We must hurry up, byebye!
J:ya.... see you soon!
M:See you.