| siffloter | whistle |
| Sifnos | Sifnos |
| sifu | sifu |
| SIG | geographic information system |
| Siganus vulpinus | Foxface rabbitfish |
| SIGARMS | SIG SAUER |
| Sigeberht | Sigeberht of Wessex |
| Sigebert | Sigebert |
| Sigebert de Gembloux | Sigebert of Gembloux |
| Sigebert Ier | Sigebert I |
| Sigebert II | Sigebert II |
| Sigebert III | Sigebert III |
| Sigebert le Boiteux | Sigobert the Lame |
| Sigefroy de Luxembourg | Siegfried of Luxembourg |
| Siger de Brabant | Siger of Brabant |
| Sigfrid Edström | Sigfrid Edström |
| Siggraph | SIGGRAPH |
| Sighetu Marmaţiei | Sighetu Marmaţiei |
| Sighişoara | Sighişoara |
| sigillographie | sigillography |
| Sigirino | Sigirino |
| Sigirîya | Sigiriya |
| sigisbée | beau |
| Sigismond | Sigismund of Burgundy |
| Sigismond Ier Báthory | Sigismund Báthory |
| Sigismond Ier de Pologne | Sigismund I the Old |
| Sigismond II de Pologne | Sigismund II Augustus |
| Sigismond II Rákóczi | Sigismund Rákóczi |
| Sigismond III de Pologne | Sigismund III Vasa |
| Sigismond Malatesta | Sigismondo Malatesta |
| Sigismund Thalberg | Sigismond Thalberg |
| Sigiswald Kuijken | Sigiswald Kuijken |
| Sigles de trois lettres | Three letter acronym |
| Siglistorf | Siglistorf |
| Siglufjörður | Siglufjörður |
| Sigma | Sigma |
| Sigma Corporation | Sigma Corporation |
| Sigma Librae | Sigma Librae |
| Sigma Octantis | Sigma Octantis |
| Sigma Olomouc | SK Sigma Olomouc |
| Sigma Sagittarii | Sigma Sagittarii |
| Sigma Scorpii | Sigma Scorpii |
| Sigmar Polke | Sigmar Polke |
| Sigmaringen | Sigmaringen |
| Sigmaringendorf | Sigmaringendorf |
| Sigmodontinae | New World rats and mice |
| Sigmund Freud | Sigmund Freud |
| Sigmund Jähn | Sigmund Jähn |
| Sign of the Hammer | Sign of the Hammer |
| Signac | Signac |
| signal | signal |
| Signal BOLD | Blood-oxygen-level dependent |
