Odd lot and board lot are terms used in the context of trading securities, such as stocks or bonds, and they refer to different quantities of shares that investors can buy or sell. Here's a breakdown of the key differences between these two terms:

1. Quantity of Shares:
- Odd Lot: An odd lot represents a quantity of shares that is less than the standard trading unit or board lot for a particular security. It typically consists of fewer shares than what is considered a standard trading lot.
- Board Lot: A board lot, on the other hand, refers to the standardized quantity of shares that can be traded on an exchange. It is typically a larger number of shares and is determined by the exchange where the security is listed. Board lots are established to promote orderly trading.

2. Pricing:
- Odd Lot: Because odd lots are smaller quantities of shares, they may sometimes incur slightly higher trading costs per share due to differences in transaction fees or spreads. This can be a disadvantage for investors trading odd lots.
- Board Lot: Board lots often have more favorable pricing because they are traded in larger quantities, which can result in lower transaction costs per share.

3. Marketability:
- Odd Lot: Odd lots may be less marketable because they represent unconventional and non-standard quantities of shares. As a result, they may not be as actively traded, and finding a counterparty for an odd lot trade can sometimes be challenging.
- Board Lot: Board lots are considered more marketable because they conform to standard trading units. They are more likely to have active trading activity, which makes it easier for investors to buy or sell them.

4. Investor Preferences:
- Odd Lot: Some individual investors may find odd lots more accessible because they require a smaller capital outlay. However, professional and institutional investors typically prefer to trade in board lots due to their liquidity and standardized nature.
- Board Lot: Institutional investors and traders often prefer board lots because they can efficiently trade larger quantities of shares, making it easier to manage their portfolios.

The primary difference between odd lots and board lots lies in the quantity of shares being traded. Odd lots represent non-standard, smaller quantities of shares, while board lots are standardized quantities determined by the exchange. The choice between trading odd lots or board lots depends on an investor's preferences, trading strategy, and the liquidity of the securities being traded.