In this subtitle the following words have the meanings indicated. “Building” includes any unit of a nonresidential building that is leased or separately sold as a unit. “Contract” means an agreement of any kind or nature, express or implied, for doing work or furnishing material, or both, for or about a building as may give rise to a lien under this subtitle. “Contractor” means a person who has a contract with an owner. “Land” means the land to which a lien extends under this subtitle or the land within the boundaries established by proceedings in accordance with the Maryland Rules. “Land” includes the improvements to the land. “Owner” means the owner of the land except that, when the contractor executes the contract with a tenant for life or for years, “owner” means the tenant. “Subcontractor” means a person who has a contract with anyone except the owner or his agent.