Certain terms are used so often in the Landlord/Tenant world that a shorthand has developed. It's often used in court, but also on this board. These are some of the more popular abbreviations or acronyms.
OP = Original Poster (starts a thread on the forum)
LL = landlord (sometimes just "L")
Ten = tenant (sometimes just "T")
LL/T = Landlord/Tenant
RC = Rent Control
RS = Rent Stabilized
RR = rent regulated
DHCR = New York State Division of Housing and Community Renewal
MCI = Major Capital Improvement
RGB = Rent Guidelines Board
PAR = Petition for Administrative Review
A78 = Article 78 (a judicial appeal in NYS Supreme Court under Article 78 of the CPLR challenging a decision of DHCR.
CPLR = Civil Practive Law and Rules (compilation of New York State Procedural Law)
RSL = Rent Stabilization Law
RSC = Rent Stabilization Code
MDL = Multiple Dwelling Law
MRL = Multiple Residence Law (like MDL for upstate areas)
HMC = Housing Maintenance Code
HPD = NYC Dept. of Housing, Preservation and Development
ETPA = Emergency Tenant Protection Act (1974) that allows municipalities to opt into rent stabilization. Must be renewed periodically.
RRR = Return receipt requested
PT = Prime tenant
RO = rent overcharge
IT = illusory tenant or illusory tenancy
SOL = Statute of Limitations
S.O. (usually with periods: "So Ordered" when a judge signs a decision or stipulation)
Stip = shorthand for Stipulation, often to adjourn cases but also can be used to "stipulate to the facts" of a case.
SRO = Single Room Occupancy
ML = Mitchell Lama
ST = subtenant
RM = Roommate
MTM = Month to Month (can be M-T-M or M2M)
SCC = Small Claims Court
MBR = Maximum Base Rent (used for RC)
MCR = Maximum Collectible Rent (used for RC)
O/T = Off Topic, usually a topic not dealing with tenant issues.
Some abbreviations are taken from the DHCR shorthand for assigning docket numbers to cases ... usually the last two letters. See http://tenant.net/DHCR_info/pubs/docket.html
Internet Terms (there are many more, but here's a few)
IMO or IMHO = In [my] Humble Opinion
FYI = if you don't know then you need help
RTFM = Read the F'ing Manual
BTW = By the Way
AFAIK = As far as I know
ROTFL = Rolling on the floor laughing
In all honesty, some of these are not used all that often, but others are. If you have others, add a reply here and periodically we'll update the master list. But please, don't invent acronyms if it doesn't really exist.