Page 151. " But they were still alive, building a new red-earth and thatch house for their teacher, Mr. Kiaga "
Njem house in Cameroon.jpg
GNU Free Documentation LicenseNjem house in Cameroon.jpg - Credit: Amcaja

A thatch house is usually made from red mud, clay, bamboo, wood, and palm fronds.  It is used as a family home (contains a kitchen, bedroom, etc.). 

Page 152. " he felt a strong desire to take up his machete "

A machete is a large heavy knife generally used as a weapon or an implement for cutting.

Page 154. " If a gang of efulefu decided to live in the Evil Forest it was their own affair. "

The Evil Forest was a forest on the outskirts of Umuofia.  The Igbo people feared the forest, especially at night. The outcasts (osu) lived closest to it.  The Igbo threw twins or people with disease into the forest because they were thought of as evil.

Page 154. " When one came to think of it, the Evil Forest was a fit home for such undesirable people. "

The undesirables referred to are known as Efulefu in the Igbo language.  It translates literally to "woman" and was used as a derogatory name for worthless or weak men.  In this case, Okonkwo uses it to refer to the men that had abandoned the traditions of the tribe to embrace Christianity and join the European missionaries.

Page 156. " He [osu] was a person dedicated to a god, a thing set apart - a taboo for ever, and his children after him. "

The osu were outcasts in Igbo society.  They lived on the edge of the forest and were not allowed to cut their hair.  They could not take titles and were not allowed to marry or take shelter with a normal Igbo person.  Many of the osu saw the new Christian church as a place for refuge and as a place to be accepted. 

Page 163. " Ekwefi still had some cassava left on her farm "
Cassava
Public DomainCassava

A cassava is an edible, startchy, tuberous root.

Page 164. " and a little hoe for digging out the tuber. "
Potato
Public DomainPotato

A tuber is a plant with an englarged root. A potato is one of the most common kinds of tubers.

Page 171. " The clan was like a lizard "

One of the most common lizards in Nigeria is the appropriately named Nigerian Spiny-Tailed Lizard. They have a stocky build and a well-armored tail which gives it its common name.

If you would like to have one in your house, visit this website for pet information.

Page 172. " Ozo society "

Nze na Ozo Society  is a traditional patriarchal institution that confers the Ozo title to deserving, qualified men; generally these men and boys derive from wealthy families. Members abide by moral codes of truth, justice, and fairness, as reflected by the bonds their words of loyalty represent and the sacred uprightness of the position they uphold in the community. The Nze na Ozo Society live by the Igbo maxim, Eziokwu bu Ndu (truth is the basis of existence), and care for everything that is sacred and traditional in a community.

The Nze (an inductee of the Nze na Ozo Society) maintains the highest position in the social hierarchy of their respective town. The process to become formally initiated requires many steps: a) a nod from the patrilineal family; b) approval of his kindred through an elaborate spiritual and secular convivial ceremony; c) further ceremonies at the village level; d) public conferment, declaration, and celebration of the induction into the Nze na Ozo Society; and e) the assumption of a new, dignified name.

Page 173. " offers of marriage "

In the Igbo culture, marriage occurs between a man and woman not long after puberty. A man can take multiple brides as long as he can pay their bride-price. A woman's primary duty in marriage is to give birth to a son. Therefore, fertility is extremely important to both women and men. Often, marriage is seen as a way of advancing in society, or result of a business relationship, and is not a result of traditional love.