Base Year: A 12 month period which is the basis for determining expenses; most often the initial 12 month period, the base year can be negotiated to other 12 month periods to secure expense relief.  
Example: Often in a multi-year lease a base expense level is determined by calculating the expenses incurred during the base year. 

Build-Out: The process of finishing out the raw space of a building.
Example: New commercial tenants often do not realize the costs associated with the build-out of their leased space.  This often affects their ability to get fair TI concessions. 

CAM/Common Area Maintenance: The additional rent charged as an expense to the tenant, commonly pro-rated to maintain the common areas of the building. 
Example: Our building CAM charges include security, janitorial, and landscaping services.

Expense Stop:  A fixed dollar amount agreed upon by the landlord and the tenant above which the tenant is responsible for all building expenses.
Example: The expense stop, best understood as the landlord expense stop, is a set dollar amount where the landlord stops paying expenses.  

Holdover: A tenant that remains in possession of the property after their lease has expired.
Example: Anytime a tenant remains in leased space without an extension or renewal they are considered a holdover and are subject to the terms of the lease’s last period.

Option to Renew: An option found in most leases which allows the tenant to extend the lease once the  primary term has expired.
Example: A fast growing firm taking a conservative leasing approach might opt to take a shorter lease with an option to renew. This allows the tenant flexibility if the business expands too fast or takes an unfortunate downward turn.

Sublet: When a sub-lessor transfers a portion of their leasehold interest to another person or entity. 
Example: The subletting of the property will not eliminate the financial responsibility of the sub-lessor (original lessee) but may significantly reduce their financial burden.

Subordination Clause: A clause in a lease by which the entity with an interest in real estate consents to a reduction in priority with regard to another person or entity holding an interest in the same real estate.
Example: Most tenants of new construction will be required to sign a lease with a subordination clause that will prioritize the liens of the developer’s lenders ahead of any interest of the tenant. ,/i.