| proving |
| provisionary(adjective, unsettled, temporary, tentative, speculative) |
| provisory |
| radical(new, modern, pioneering, trailblazing, secretive) |
| rational(reasonable, useful, realistic, reasoning, intellectual) |
| realistic(reasonable, useful, applied, hands-on, real-world) |
| reasonable(useful, realistic, reasoning, intellectual, mental) |
| research |
| resolute |
| sane(reasonable, useful, realistic, reasoning, intellectual) |
| sensible(reasonable, useful, realistic, reasoning, intellectual) |
| serviceable(adjective, reasonable, sensible, useful, sober) |
| sober(reasonable, useful, realistic, reasoning, intellectual) |
| solid(reasonable, useful, realistic, applied, hands-on) |
| sound(adjective, reasonable, sensible, rational, useful) |
| stopgap(extra, temporary, auxiliary, tentative, contingent) |
| substitute(adjective, extra, alternative, auxiliary, supernumerary) |
| systematic(adjective, reasonable, sensible, useful, sober) |
| try |
| trying |