(a) Sign. An outdoor sign, light, display, device, figure, painting, drawing, message, placard, poster, billboard or other thing which is designed, intended of the advertising or informative contents of which is visible from any place on the main-traveled way of the Interstate or Primary Systems, whether the same be permanent or portable installation.

(b) Lease (license, permit, agreement, contract or easement). An agreement, oral or in writing, by which possession or use of land or interests therein is given by the owner or other person to another person for a specified purpose.

(c) Leasehold value. The leasehold value is the present worth of the difference between the contractual rent and the current market rent at the time of the appraisal.

(d) Illegal sign. One which was erected and/or maintained in violation of State law.

(e) Nonconforming sign. One which was lawfully erected, but which does not comply with the provisions of State law or State regulations passed at a later date or which later fails to comply with State law or State regulations due to changed conditions. Illegally erected or maintained signs are not nonconforming signs.

(f) 1966 inventory. The record of the survey of advertising signs and junkyards compiled by the State highway department.

(g) Abandoned sign. One in which no one has an interest, or as defined by State law.