1. Costing nothing
   - complimentary, free, gratis, gratuitous

See also: unpaid

• yellow-green algae
• yellow-grey
• yellow-leaf sickle pine
• yellow-marked
• yellow-orange
• yellow-shafted flicker
• yellow-spotted
• yellow-striped
• yellow-throated marten
• yellow-tinged
• yellow-tipped
• yellow-white
• yellowbelly marmot
• yellowbird
• yellowcake
• yellowed
• yellowfin
• yellowfin croaker
• yellowfin mojarra
• yellowfin tuna
• yellowhammer
• yellowish
• yellowish brown
• yellowish green
• yellowish pink