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# Semi|Definition & Meaning

## Definition

Semi **literally** means “half.” It is used as a prefix to imply halves of various things. For **example, semi-annually** means every half-year (e.g., interest **compounding), semicircle** means a half **circle,** and **semi-major** and **minor** axes mean half the major and **minor** axes of ellipses. It is also used in other contexts, as in semiprime numbers (a **product** of two **prime** numbers).

A **prefix** that **means** “half” is known as a **semi.** The most common **example** of the semi is a **semi-circle** and semiannually. Let’s first **explain** the semi-circle in **detail.** The following figure represents the **semi-circle.**

Figure 1 – Representation of semi-circle

The **figure** below **represents** the semi-polygon.

Figure 2 – Semi-polygon representation

## What Is a Semi-circle?

A **semicircle** is a half-circle **created** by **splitting** a **circle** into two equal parts. It is created when a line pierces the circle’s **center** and **touches** its two ends. The circle’s **diameter** is the name **given** to this line.

Taking a **whole** circle and **slicing** it in half along its diameter yields a **semicircle,** which can also be referred to as a half-circle. Only one **line** of **symmetry,** known as the reflection **symmetry,** may be found in the shape of a **semicircle.** A **half-disk** is another **name** for a shape that **resembles** a semicircle.

Since a **semicircle** is only half of a circle, its arc will always measure 180 degrees **because** 360 degrees is the total **number** of degrees in a circle.

Figure 3 – Circle representation

**Finding a Semicircle’s Area**

The **interior** or the **surrounding** area of such a **semicircle** is referred to as its area. It has a circle’s half surface area. **Remember** that a **circle’s** area is **equal** to πr², where the circle’s radius is denoted by r and pi (π) is approximately equal to 22/7 = 3.14. Thus, the **following equation** can be used to determine a semicircle’s area:

**Area of semi-circle is = ½ × πr²**

**Finding a Semicircle’s Circumference and Perimeter**

The perimeter or **circumference** indicates the length of the semicircle’s entire boundary. **Contrary** to popular belief, a semicircle’s perimeter is not equal to half that of a circle **because** a circle’s **half-perimeter** only yields the curved portion’s perimeter. The bottom diameter line must be added to the bottom circumference to get the whole **perimeter.**

Remember that a **circle’s** radius is 2πr. **Therefore,** the circumference of the semicircle’s curved portion is equal to 1/2 of 2πr equal to πr. Let’s now provide the diameter’s length as well, so the semicircle’s total **perimeter** is equal to πr + d, where d is its **diameter.**

**However,** we are also aware that a **circle’s diameter** is equal to twice its radius. As a result, we find that the semicircle perimeter is equal to πr + 2r. We can take r **common,** so the perimeter = r (π + 2).

**Characteristics of a Half Circle**

The **following** is a list of some essential characteristics of a semicircle, which together make it a **distinctive** form in geometry:

A closed

**two-dimensional**shape is known as a semicircle.Due to the fact that one of its

**edges**is bent, it cannot be**considered**a polygon.One of the

**edges**of a**semicircle**is curved, and this edge is known as the**circumference.**The other edge is straight, and this edge is known as the**diameter.**It

**corresponds**to**precisely**one-half of a circle. Both semicircles that were generated out of the circle had the same diameter as the circle**itself.**A

**semicircle**has an area**equal**to one-half that of a full circle.

## What Is a Semi-Annual?

The word **“semiannual”** designates events that **occur twice** a **year,** often once every six **months,** and are paid for, reported, published, or take place in another manner.

For instance, the interest on a **general** obligation bond with a term of **ten** years that was issued in 2020 by **Buckeye** City, Ohio Consolidated School **District** will be paid on a **semiannual** basis each year up to the maturity date of the bond in 2030.

When an **investor** purchases **these** bonds, he or she will be entitled to interest payments twice during each of those years, **specifically,** once in the month of June and once in the month of **December.** The school system will also issue a **semiannual** financial report in **February** and November.

**A Detailed Explanation of Semi-Annual**

The term **“semiannual”** refers to something that takes place **twice** yearly and is merely a word. For instance, a business may hold **workplace** parties on a **semiannual** basis, a couple could celebrate their marriage **anniversary** on a semiannual basis, and a family could take a vacation on a **semiannual** basis. The term **“semiannual”** refers to **occurrences** that take place twice yearly.

If a **company** decides to pay its **shareholders** a dividend on a semiannual basis, then those **shareholders** will be entitled to dividend **payments** on two separate occasions each year. A corporation has the ability to **decide** whether or not to deliver dividends on an **annual** basis. Quarterly (or four times a year) publications of financial statements or perhaps even reports are common practice.

It is quite **unusual** for **companies** just to **publish** their **financial** results every other year. However, they do provide an annual report, which, **according** to the dictionary definition, must be done at least once every year.

When **purchasing** bonds, it is **essential** to have a solid **understanding** of the semiannual payment schedule. The yield that a bond pays its holder is typically used as a way to characterize the bond. A **bond** with a face value of **$2,000** might have a yield of 5%, for instance.

To have a better **understanding** of the payment that you would get as the **bondholder,** it’s indeed essential to understand if this 5% has been paid **annually** or semiannually.

## A Numerical Example of a Semi-circle

### Example 1

A **semicircle** has a **diameter** of 7 cm. **Determine** the curved surface’s **perimeter.**

### Solution

**Given** that:

The circle has a **7 cm** diameter.

**Radius = 7/2 cm.**

Semicircle’s curved surface’s perimeter is equal to 1/2 * 2πr.

=** ½ × 2 × 22/7 × 7/2**

**= 11 cm**

### Example 2

A **semicircle** has a diameter of 8 cm. **Determine** the curved surface’s **perimeter.**

### Solution

**Given** that:

The circle has a 7 cm **diameter.**

**Radius = 8/2 cm.**

**Semicircle’s** curved surface’s perimeter is equal to 1/2 * 2πr.

**= ½ × 2 × 22/7 × 8/2**

**= 12.56 cm**

*All mathematical drawings and images were created with GeoGebra.*