The word for comfortable in Spanish is cómodo for masculine nouns and cómoda for feminine nouns. When describing a masculine object or person, you would use ‘cómodo’; for a feminine object or person, you would use ‘cómoda’.
For example, you might say: Este sofá es muy cómodo (This sofa is very comfortable) or Esta silla es muy cómoda (This chair is very comfortable).
The pronunciation is also important; it can be represented phonetically as /ˈko.mo.ðo/ for the masculine form. Remember that in Spanish, adjectives must agree in gender and number with the nouns they describe, so make sure to use the correct form based on the context!