GM is using greek letters to denote the platforms... in this case lambda.
other platforms are
some of the cars on these platforms are mentioned (theres more in each)
theta- saturn vue, Pontiac torrent,equinox- etc
delta- Ion, HHR
gamma-Corsa, Meriva
kappa-Sky, Solstice
sigma-Caddy CTS, SRX
zeta-2010 camaro, 2006 Caprice, Buick park avenue
alpha- to come in 2012.
theres also alot of other platforms that dont use the greek alphabet-- like the GMT-360- which are the platform for the Trailblazer. Envoy. Bravada. Ascender. etc.
on an interesting note--- the solstice- shares alot from different cars...
The Kappa architecture uses major components from nearly every GM division and modern platform:
The rear axle and differential are from the Sigma-based Cadillac CTS
The Solstice's interior storage bin is from the Y-body Cadillac XLR
The passenger-side airbag, steering column, and exterior and interior door handles are from the Delta-based Chevrolet Cobalt, Pontiac G5
The Solstice's backup lights are from the GMT360 GMC Envoy
The heating, ventilating, and air conditioning modules are from the Hummer H3
The Solstice's front fog lamp assembly is from the W-body Pontiac Grand Prix
The Solstice's steering wheel is from the Delta-based Pontiac G5
The 2.4 L Ecotec engine is shared with the Delta-based Saturn Ion, Pontiac G6, Chevrolet Cobalt, Pontiac G5, and Chevrolet HHR
The five-speed manual transmission is from the Hummer H3, GMC Canyon, and Chevrolet Colorado
The five-speed automatic is from the Cadillac CTS, STS, and SRX