These three are searched interchangeably and are not interchangeable.
Grant
The government gives you money to accomplish a public purpose. You propose the work; they fund it because it serves a policy goal.
Minimal government involvement in how you do it. Reporting obligations, restricted use of funds, and — above $1 million in federal funds expended in a year — a Single Audit.
Contract
The government buys a deliverable from you. They specify what they want; you supply it and get paid.
You are a vendor, not a beneficiary. This is a commercial relationship with acceptance criteria, and it is where most government money actually goes.
Cooperative agreement
A grant with substantial government involvement in carrying out the work. The agency is an active participant — approving plans, joining decisions — rather than just funding and monitoring.
If you see “cooperative agreement”, expect a relationship, not a cheque.
Why it matters practically
Eligibility differs. Many grant programs are limited to nonprofits, governments or institutions. Contracts are generally open to any capable vendor, with set-asides favoring certified small businesses.
Effort differs. A proposal argues merit. A bid demonstrates capability and price.
Obligations differ. Grants carry Uniform Guidance compliance. Contracts carry performance terms.
In OpenGrants
Grants and contracts are separate databases with separate searches and separate filters — contracts add NAICS, set-aside and value band. Searching the wrong one is the most common reason people conclude something is not in the corpus.
See Searching government contracts and RFPs.
Going deeper
The full mechanics — appropriation to NOFO to merit review to closeout — are in How federal grant funding actually works.