Fixed Rate Gilt/Conventional Gilt:
A Gilt where the interest rate you receive is fixed from the start, e.g. Treasury 5% 2012.
Index-linked Gilt:
A Gilt where the interest rate (and the final capital value) you receive is influenced by inflation, e.g. Index-Linked Treasury 2½% 2016.
Nominal value:
the face value or amount of the Gilt, and the capital amount you receive on redemption of a Fixed Rate Gilt.
Uplifted Nominal value:
The nominal value of Index-Linked Gilts adjusted by inflation since the Gilt was issued.
Consideration:
The price you pay / receive on purchase / sale, including an element for accrued interest.
Redemption date:
The date on which your capital is repaid to you. Most conventional Gilts have a specific redemption date; for details visit www.dmo.gov.uk/gilts/data/f2dat.htm.
Dated Gilts:
A Gilt where there is a firm redemption date, e.g. Index-Linked Treasury 2½% 2016.
Undated Gilts:
A Gilt where there is no stated redemption date, e.g. War Loan 3½%.
Double-dated Gilts:
A Gilt where the Government chooses the exact timing of redemption, at a point between the two dates shown, giving 3 months notice, e.g. Treasury 7¾% 2012-2015.
Short-maturity Gilt:
A Gilt with up to 5 years to maturity.
Medium-maturity Gilt:
A Gilt with between 5 and 15 years to maturity.
Long-maturity Gilt:
Gilts with more than 15 years to maturity.
The coupon:
The annual rate of interest paid on the Gilt, usually in two equal, half-yearly installments. Interest is expressed as a percentage of £100 nominal, e.g. Treasury 5% 2012.
Accrued interest:
The amount of interest earned on a Gilt since the last interest payment date, which is paid /received in addition to the 'clean' price at the time of buying /selling the stock. The exception to this is when you buy once the Gilt has gone 'ex-div': in this circumstance you are not entitled to the interest payment and hence accrued interest is deducted from the price. You will, however remain entitled to the accrued interest if you sell after the 'ex-div' date.
Clean price:
The quoted price of the Gilt excluding the value of accrued interest. It is this price which is usually quoted in newspapers; except when trading in ex-div Gilts, you will need to add the value of accrued interest to the clean price in order to calculate the overall consideration / receipts.
Dirty price:
The total price paid / received on a Gilt, equating to the clean price plus an adjustment for accrued interest.
Interest yield/Flat yield:
Your income based on the actual purchase price of the Gilt, rather than the nominal value. Calculated by dividing the coupon by the current price.
Redemption yield:
The total return if you hold the Gilt to maturity. Includes an adjustment for the effect of a price moving closer to the nominal value as the maturity date draws nearer.
Flat Yields and Redemption Yields are published in daily newspapers such as the Daily Telegraph, and you can use these to assess the regular income and total return you will receive on your investment.
When it comes to Undated Gilts (such as War Loan 3½%.), it is unlikely they will be redeemed, and so they are best assessed with reference to their Flat Yield only.
Let's illustrate investment in Gilts with a couple of examples:
Conventional (Fixed Rate) Gilts example 
Say you invested £1,000.00 (excluding dealing commission) in Treasury 7¾% 2012-2015 at a price of £119.25p (plus accrued interest), on 15/9/2005.
Your £1,000 would have bought you £830.00 nominal of stock in this Gilt.
This is calculated as follows:
the amount you want to invest (£1,000.00) divided by the Market price (£119.25) plus 56 days of accrued interest of £9.788.
There is no Stamp Duty payable on Gilts and your dealing commission, based on the total consideration at the Standard Share Account tariff, would be £9.99.
Whilst the coupon is 7¾%, the 'flat yield' on your investment would have been 6.43%: this is calculated by dividing the coupon rate (7¾%) by the purchase price (£119.25 + £1.79), reflecting the fact that you've paid £121.04 for every £100 of nominal value.
While the market price may rise and fall over the intervening years, your holding will eventually be redeemed at £100 if you hold it to maturity. The Government chooses exactly when to 'redeem' the stock between 2012 and 2015: if they can borrow equivalent money cheaper, they will probably redeem earlier: if borrowing costs at the time are higher than 7¾%, it's more likely to be the later date.
So your total return to maturity (the 'Redemption Yield') includes both your 'Flat Yield' and a negative adjustment for the annual effect of the price reducing from £119.25 to £100 over the next 7-10 years.
As regards market price movements, the key point to remember about Gilts is that if their Redemption Yield rises, the price falls - and vice versa. So your expectations for long-term interest rates are critical to your investment decisions.
Index-linked Gilts example 
These operate completely differently to Fixed Rate Gilts, because both the interest payments and the redemption amount are primarily influenced by inflation.
Say you now invest £1,000.00 (excluding dealing commission) in Index-linked Treasury 2½% 2016 at a market price of £256.15 (plus accrued interest), on 15/9/2005. Your £1,000 would have bought you £389.00 nominal of stock in this Gilt.
This is calculated as follows:
the amount you want to invest (£1,000.00) divided by the Market price (£256.15) plus 56 days of accrued interest of £3.48.
There is no Stamp Duty payable on Gilts and your dealing commission, based on the total consideration at the Standard Share Account tariff, would be £9.99.
This time, however, the calculations to determine Flat Yield and Redemption Yield are significantly more complex.
The coupon rate is adjusted for the movement in the Retail Price Index since its launch, whereas the Redemption amount has also been, and will continue to be, adjusted by inflation/deflation over the years to maturity.
To be more precise, each Index-Linked Gilt has an 'index number' that relates to its base index, i.e. the level of the Retail Price Index (RPI) 8 months before the Gilt was first issued. The value of interest payment and the final capital repayment can be calculated by comparing the base index with the level of the RPI 8 months before payments are due.
However, so far as market price movements are concerned, you should bear in mind that Index-linked market prices vary with the market's expectations on inflation: prices tend to rise if there's an expectation of higher inflation.
Keeping track of Gilt prices
Prices are quoted in the financial press and there is a regular section in the FT Companies and Markets section every Saturday. Prices are also shown on many investor websites, including Bondscape (www.bondscape.net). Price histories can be accessed via the DMO website (www.dmo.gov.uk).
Normally we’ll show the last closing price in your account, where this isn’t available call our dealers for the latest price.
Bid/offer spreads apply to trading in Gilts as they do for equities but are generally much tighter; it is not unusual to deal on spreads of just 10p per £100 of stock.