The term "security" is defined broadly to include a wide array of investments such as stocks, bonds, notes, debentures, limited partnership interests, oil and gas interests, and investment contracts. Generally, an "investment contract" is created when a person invests something of value (usually, money) in a common enterprise with the expectation of a return (e.g., dividends or increased capital) to come through the managerial efforts of someone other than the investor.

Thus, the definition of security found in Section 4.A. of the Texas Securities Act does not list every form of security that may exist. A security may exist even if there is no written document.

The term "security" or "securities" shall include any limited partner interest in a limited partnership, share, stock, treasury stock, stock certificate under a voting trust agreement, collateral trust certificate, equipment trust certificate, preorganization certificate or receipt, subscription or reorganization certificate, note, bond, debenture, mortgage certificate or other evidence of indebtedness, any form of commercial paper, certificate in or under a profit sharing or participation agreement, certificate or any instrument representing any interest in or under an oil, gas or mining lease, fee or title, or any certificate or instrument representing or secured by an interest in any or all of the capital, property, assets, profits or earnings of any company, investment contract, or any other instrument commonly known as a security, whether similar to those herein referred to or not. The term applies regardless of whether the "security" or "securities" are evidenced by a written instrument. Provided, however, that this definition shall not apply to any insurance policy, endowment policy, annuity contract, optional annuity contract, or any contract or agreement in relation to and in consequence of any such policy or contract, issued by an insurance company subject to the supervision or control of the Texas Department of Insurance when the form of such policy or contract has been duly filed with the Department as now or hereafter required by law.