---
title: Title-case a single word
summary: Apply acronym/lowercase/mixed-case/ordinal rules to one word.
status: draft
owner: saif-docgen
last_reviewed: 2026-09-15
library: SAIF.Framework.Common
reference_type: package
operation_id: OP-002
trigger: Called once per split word by OP-001 step 4
---

# Title-case a single word

Apply acronym/lowercase/mixed-case/ordinal rules to one word, triggered when called once per split word by OP-001 step 4.

| Field | Value |
| --- | --- |
| **Operation ID** | OP-002 |
| **Trigger** | Called once per split word by OP-001 step 4 |
| **Inputs** | `string inWord` |
| **Outputs** | Cased `string` |
| **Primary components** | ``TitleCase.TitleCaseSingleWord(string)` (private)` |
| **Entry point** | `Common/SAIF.Common/Utility/TitleCase.cs` |

## Steps

1. If the word already contains both an uppercase and a lowercase character, return it unchanged — it is assumed intentionally cased. ([BR-015](../business-rules.md#br-015-a-word-that-already-contains-both-uppercase-and-lowercase-characters-is-assumed-intentionally-cased))
2. Else if the uppercased word is in `UpperCaseWordList` (SAIF, KPD, BW, AIC, LLC, LLP, DDS, MD, II, III, IV, NE, NW, SE, SW, PO, USA, CA, WA, OHSU), uppercase the whole word. ([BR-016](../business-rules.md#br-016-words-in-the-approved-acronym-list))
3. Else if the lowercased word is in `LowerCaseWordList` (`is, in, the, an, of, on, and, de`), lowercase the whole word. ([BR-017](<../business-rules.md#br-017-minor-words-(is%2C-in%2C-the%2C-an%2C-of%2C-on%2C-and%2C-de)-are-rendered-fully-lowercase>))
4. Else if the lowercased word matches an entry of `MixedCaseWordList` (`PhD`, `LaCombe`), substitute that entry's exact casing. ([BR-018](<../business-rules.md#br-018-known-mixed-case-words-(phd%2C-lacombe)-keep-their-exact-registered-casing>))
5. Else if the word is digits plus an ordinal suffix (`HasNumberSuffix`: digit-only stem plus one of `NumberSuffixes`), keep the ordinal suffix lowercase. ([BR-019](<../business-rules.md#br-019-a-numeric-word-with-an-ordinal-suffix-(1st%2C-2nd%2C-3rd%2C-4th)-keeps-the-suffix-lowercase>))
6. Else apply `StringExtensions.ToProperCase` (current-thread culture `TextInfo.ToTitleCase` over the lowercased word).
7. If the result starts with a `MixedCasePrefixList` prefix (`Mc`, `O'`), split at the prefix and proper-case the remainder so `mcmahon` becomes `McMahon`. ([BR-018](<../business-rules.md#br-018-known-mixed-case-words-(phd%2C-lacombe)-keep-their-exact-registered-casing>))

## Process flow

The following diagram visualizes this operation's control flow.

```mermaid
flowchart TD
	Start(["Called once per split word<br>by OP-001 step 4"]) --> D1{"Contains both upper and<br>lower case characters?"}
	D1 -->|Yes| R1["Return word unchanged"]
	D1 -->|No| D2{"Uppercased word is in<br>UpperCaseWordList?"}
	D2 -->|Yes| R2["Uppercase the whole word"]
	D2 -->|No| D3{"Lowercased word is in<br>LowerCaseWordList?"}
	D3 -->|Yes| R3["Lowercase the whole word"]
	D3 -->|No| D4{"Lowercased word matches a<br>MixedCaseWordList entry?"}
	D4 -->|Yes| R4["Substitute the entry's<br>exact casing"]
	D4 -->|No| D5{"Word is digits plus<br>an ordinal suffix?"}
	D5 -->|Yes| R5["Keep the ordinal<br>suffix lowercase"]
	D5 -->|No| R6["Apply ToProperCase<br>(current-thread culture<br>TextInfo.ToTitleCase)"]
	R1 --> D6
	R2 --> D6
	R3 --> D6
	R4 --> D6
	R5 --> D6
	R6 --> D6
	D6{"Result starts with a<br>Mc or O' prefix?"}
	D6 -->|Yes| S7["Split at the prefix and<br>proper-case the remainder"]
	D6 -->|No| End(["Cased word returned"])
	S7 --> End
```

## Related documentation
- [Operations and processes](../operations-processes.md)
- [Business rules](../business-rules.md)

## Sources
- `Common/SAIF.Common/Utility/TitleCase.cs`